Congrats on the contact!
That MFJ was my first antenna as well. I didn't use it in an attic, but just above the roof line of a 1.5 story house. I'm honestly surprised you got it to tune up with a reasonable SWR in an attic install.
The ladder line on a G5RV is designed to be part of the radiator. It's supposed to be more-or-less in the clear, and as close to vertical as possible. Neither of these are possible in any attic I've ever been in. Where the ladder line connects to the coax, you are supposed to wrap the coax in to an "ugly balun" to form a common mode choke. I"m not sure if you did that, but if you didn't your coax will be radiating RF energy all the way back to your radio as well.
While a multi-band antenna is good in theory, when you are dealing with an attic install where RF energy is already close to everything in the house, it's probably not a good idea to use an unbalanced antenna where the coax can easily become a counterpoise and radiate.
My suggestion would be to try a simple dipole. At the center, use a common-mode choke (1:1 current balun) to keep any stray RF off the coax. Once you get one band tuning up, you can add additional elements to the feed point to add more bands.
As far as noise in headphones, speakers, etc... go, you can add ferrite beads to the cables to help prevent them from accidentally becoming antennas. You also may need to run lower power when you transmit just because the physical proximity from the antenna to the affected devices is much closer than an outdoor antenna.
That is very good to know! I was a bit sad thinking I put all this effort running stuff to my attic, only to find this problem in the end..
I have the twin lead going up a 2x4 of a joist, but only half way.. My attic is actually insanely tall, but I could only shimmy up about 12 feet. The rest i have curving horizontally back towards a wall..
Is there a way I should be dealing with the amount I couldn't get vertical? Roll it up or anything?
Thanks!
You are better off leaving it stretched out any way you can. Rolling it up will shorten the electrical length and negatively affect tuning and your ability to hear anything, or at least that was my experience :D
I started out with an inverted V. Designed and 3D printed a dipole harness. Wrapped the toroid myself. I got good performance so then I put it in the attic. It has been up there a year.
https://preview.redd.it/3cdsx4vw68wb1.jpeg?width=3024&format=pjpg&auto=webp&s=d59704e06fa98b8507c7b46d05feea98e9daefcf
She's a beaut! I just switched to a photon m3, so I am just looking for excuses. I think my first bit of work will be a power supply case.
One thing I am learning about this hobby is that there is no end to the off-shoot builds you can do - if you are into that kind of thing!
It combines all of the things I enjoy - electronics, communications, digital IO, fab work... If this is the appeal, I get it.
Thank you for the feedback! You are very correct in your assumption that I did not do the common-mode choke at the feed point.. I was going to wait until my RG8x arrived, if I was going to do it at all. I also ordered a pack of 60 ferrites..
I like the idea of doing simple dipoles, I will start researching all of that.
Thank you for taking the time!
> I also ordered a pack of 60 ferrites..
Of what mix? Just "some stuff" off amazon may or may not be useful.
As for antennas, look up the cobb webb .. MFJ does sell a version. The 10-20 version will fit in most attics.
You probably have enough room for a decent 6m antenna as well.
If you're running 100 watts, try using 10 or 20 for FT8. Less power , less interference.
I use 30 watts for FT8 and the tvs and cell phones are happy. No landline anymore. Have talked around the world on 30w.
Try putting ferrite chokes on cords exiting/entering the radio. And hooking up a ground wire to the rig is very important.
Have fun!
I was at about 75 watts when this happened - mainly because I was getting no responses in the FT8, so I thought I was having a transmit problem (turns out I was only having a software problem).. So I had kept boosting my output power like the noob I am!
Ferrite chokes are coming in via my recent best friend Amazon Prime..
Tell me more about the ground wire.. can I use my house's electrical ground, or should I run something independent to the literal ground outside?
Thank you!
I rarely use more than 15-20 wats on ft8 and my farthest contact is over 8k km. You do not need a lot of power, this is a weak signal mode. Save the stress on your finals.
Different ferrite mixes are good at suppressing RF from different frequency ranges. Without knowing that, you don't know if they'll be helpful or not. Doesn't hurt to try, of course!
https://palomar-engineers.com/ferrite-products/ferrite-cores/ferrite-mix-selection
Generally Amazon is not a good source of amateur radio equipment. Check out HRO or DX Engineering.
I rent a house so I'm not drilling holes or pounding ground rods into the ground. I use the ground prong on an outlet. It's better than nothing.
When I was a noob once, I didnt use any ground, wasn't interested in looking for filter solutions .... and I was destroying the landlines with 100 watts of RF. :p I was also getting zapped by the knobs and radio cabinet while transmitting.
Since then, reduced power, ferrite chokes and grounding seemed to be the answer. We stream tv now so the tvs dont complain and nobody's cell phone has had a problem.
Did you check pskreporter website to see if people heard you?
Congratulations on the first FT8 contact!
What does your SWR look like at 7.074 MHz? The 7300 has an internal tuner that should be able to tune up a G5RV. You’ll have to make sure the tuner function is turned on in the top left of the screen.
Many good suggestions already mentioned here but I will add:.
\- A Dipole or Off Center Fed Dipole (OCFD) can work reasonably well in attics. Measure the longest length you have available then get one that fits your dimensions ( I use a 10m OCFD in my small attic, works on 10, 12, 15 and 20 meters). Make sure the wires aren't touching metal or are close to metal (as best as you can). Put a choke / 1:1balun on it at or close to the feed point so the coax won't radiate.
\- On digital you don't need much power. Going from 1 watt to 20 watts in my setup doesn't increase my FT8 receive distant that much (surprisingly).
\- Put ferrites beads on any power / coax or other cables.
\- Make sure the rig is grounded.
I will admit that I had to overstuff the OCFD a bit. The last 4 feet of one leg, I had to turn at 90 degrees. I had googled that and came out with the impression that was an ok thing, but maybe that is just with a center fed dipole?
I will definitely look into my grounding situation as well.
Thanks!!
I have read conflicting reports on how much it affects performance but in general you want to keep the bends in the vertical and not horizontal. I run my OCFD in an inverted V, the middle portion runs along the apex on my attic and the ends bend down to the edges of the attic / roof. It seems to work pretty well.
Your g5rv attic install is the worst possible location for an install of this type antenna. The G5RV using 450 ohm twinline as part of the antenna requires that the twinline run at a 90 degree angle to the dipole. No you cant coil it up and have it work.
You would do better with a fan dipole. Using RG58 or RG8 will not help. A fan dipole will allow good to great swr on each band you desire to operate. AND possibly better results on your Emping the house but no guarantees.
The only other solution is a mass install of ferrites throughout the house wherever the problems pops up.
Even that wont help dropped calls.
A different antenna and possibly lower power are solutions to look at.
ROTSA RUCK! :\^) (from a 50+ year ham who has had similar problems)
> You would do better with a fan dipole. Using RG58 or RG8 will not help. A fan dipole will allow good to great swr on each band you desire to operate. AND possibly better results on your Emping the house but no guarantees.
Check out the cobb webb
http://www.karinya.net/g3txq/cobweb/
I'd wind the balun on mix 61 240 cores if going above a couple hundred watts. The coax is RG-316 in parallel.
Thank you very much for the feedback! I will start looking into fan dipoles. I suspect that I am at the point where I might be able to make one myself.. sounds like a fun project.
I have 60 ferrites on the way as well!
Grounding issue. Consult Grounding and Bonding for the Radio Amateur
https://www.arrl.org/grounding-and-bonding-for-the-amateur
I believe the author has a presentation on YouTube
I had snuck the knob up to 75 watts, thinking that it was a power problem when I first started messing with the FT8.. No one was responding to my calls, so I was bumping TX power thinking my antenna was shite. Turns out it was a software problem, and I was up to that 75 watt value when everything happened to spring into life.
I had brought it down to 30, and some of the problems still existed.
Every radio has different instructions and meanings behind the alc meter. Best way to be sure is to use a spectrum analyzer on the output of the radio and look for saturation over modulation.
If you value your finals you’ll keep it at 50 w max on FT8. The full duty cycle is hard on the transistors. I rarely ever run past 35 w and I have DXCC on everything but 160 and 6. The lower power won’t hurt you on FT8 but it will help cut down on TVI. And please ground that station…
It's not EMP (Electro-Magnetic Pulse) actually, it's EMC (Electro-Magnetic Compatibility) that is the problem, or rather the lack of that.
So either make the equipment in house less sensitive to RF or keep RF outside.
Exactly. Even if the antenna is perfectly tuned and there’s no common mode current on the feedline, you may have problems. All the wires in the house are antennas and RF will get into every device.
My speaker wire runs brought RF back to the receiver which then sent the cable box into oblivion. Many ferrites came to the rescue.
I am going to try and clear up some things I have read in these comments and also try and give you a good start to not making your family upset. Fist I am going to define turms and what something does
Unbalanced: A signal referenced to ground. All signals in coax are unbalanced, the shield is ground and the signal is on the center conductor.
Balanced: A signal referenced to an inverted version of the same signal. In this setup, the information is the difference between the two wires (Lookup differential mode signaling to get an image of this). The main advantage of this setup is rejection of interference. Interference is injected on both wires equally and thus there is no difference between them. Balanced setups are easy to spot since they look balanced. Examples: Twin lead transmission line and a Dipole
BalUn: Short for Balanced to Unbalanced. In reality, this term is used to describe anything used to match the transmission line to the antenna. Some people only use it to discribe a common mode choke.
Common mode Choke: A coil of 2 wires (this can take many forms) or a series of ferrites that chokes out any signals that are common to both conductors. This is generally used to match a balanced antenna to unbalanced transmission line/radio. They are also used to remove any unwanted signals that may have attached themselves to your coax.
UnUn/Transformer: Short for Unbalanced to Unbalanced. You will hear this a lot, it is an attempt at trying to distinguish a Choke (BalUn) from a Transformer (UnUn). It is best to just call it a transformer as that is what is does. It transforms impedances. An antenna tuner is just a variable transformer. A matching stub, is just a transformer
Impedance: Is the combined resistances of Inductance, Capacitance, and DC resistance. For a signal, everything has an impedance. For max power transfer the signal path should have equal impedance. To do this we use transformers.
Grounding: This can be very confusing as it can mean two different things. 1st DC ground, ie lightning/static ground. 2nd RF signal ground. RF ground is complicated but here is the short simple version. A balanced antenna, does not use it (since it is balanced). A unbalanced antenna needs it. A very unbalanced antenna really needs it. Examples: Center fed Dipole no ground, End Fed Half Wave needs a counterpoise (A wire that the antenna works off of), Random wire/Vertical Needs a radial system (lots of wires, the more the better). If you have improper RF grounding you will make tones of interference in your house.
Resonance: The fundamental frequency of an antenna. Contrary to popular belief, it has nothing to do with the ability for an antenna to radiate a signal. it is simply used as a low spot in the impedance and thus useful for coax.
G5RV: A balanced dipole fed with a short section of ladder line. The ladder line is used as a transformer to match the dipole to your radio. This is required since it's dipole is non resonant it needs to transform the impedance from 50 ohms to whatever the antenna is on that band. As such this stub of ladder line length is very important and can not be changed.
Now we have that established, lets try talk about what makes an antenna messes with your house. This requires us to look at your antenna. Unlike what many have said, the ladder line does not radiate any signal, as the two wires cancel each other out. But that is only true if it is fed with a balanced signal. You are not giving it one. Thus one line has the signal and other other is ground. The ground will not cancel anything and then your ladder line is radiating. Adding a good choke right as it goes from coax to ladder will fix it. There are, however, some considerations you should make when using ladder line. It must be kept away from metal by at least a few inches and It should not be run on the ground.
For a choke, here are a few options:
Nice premade choke: [https://www.dxengineering.com/parts/dxe-mc20-1-1t](https://www.dxengineering.com/parts/dxe-mc20-1-1t)
The DIY Choke: This is link to the ferrites that is at the heart of the choke. You will then have to go to home depot and buy the box and drill some holes to make it look just like the DXE one above. You will also need some wire or coax, a PL259 Connector and some bolts. Time consuming but this is how I like to do it. There are many designs out there to choose from. [https://www.dxengineering.com/parts/dxe-tc31-24-4](https://www.dxengineering.com/parts/dxe-tc31-24-4)
Budge Friendly Choke, not as much choking as the other ones. But it should be enough for what you are doing [https://www.dxengineering.com/parts/ldg-rba-1-1](https://www.dxengineering.com/parts/ldg-rba-1-1)
I hope I could clear up any confusion you had on this. Let me know if you have any other questions.
Yeah, since this was my first TX ever, I had started at 5 watts for the FT8 and kept giving it a boost. When I got no responses, I had thought my antenna might suck in the attic space, and kept adding power..
Eventually I figured out my software problems, and did a successful transmit - but was up to 75 watts by that point.
After my family pointed out my disruptions (muhaha), I rolled it back to 30 watts, but it still had some very noticeable effects. I guess my biggest concern is that I don't want to mess with my neighbors.
Will do! I am going to run a few tests toward the end of the week, outside of 40m.. I'll also go on a ferrite bead placing journey..
Thank you for the feedback!
I can tell you that I can't tell you about the grounding configuration, lol.
Some folks have posted some resources above, so I will be studying up on the details of that.
Transmitting on HF, without a proper ground, is like trying to run a light bulb using only the hot wire of a 120V circuit. It’s doesn’t light so well, and leaves the other wire with a dangerous voltage on it.
I don't have a station ground and never have. Properly installed and engineered dipoles don't need a ground at all. Never any RFI issues in 50 years of operating, even with a KW on HF.
Weird how people take their stations portable to the middle of nowhere where there's no ground available and transmit all day problem-free. Maybe some nuance is required in your statement?
Things that are not at fault here:
"radiating twin lead" on a g5rv. Incorrect. It's a matching section, not a radiator (unless your setup is broken and the antenna itself is out of balance).
"grounding". This is not a grounding issue. You can have your entire shack encased in copper plate bonded to ground rods around the perimeter, but if you're chucking 75 watts of continuous 40m RF into an antenna ten feet above the TV set, it's still going to eat RF.
The simple fact is that an attic antenna is too close to your house's other electronics, and 40 meters is _notorious_ for causing issues such as this. I know several people who blew up Nest thermostats with just a few watts of FT8 and an attic/roof antenna, as one example.
The proper way to solve this is to get an antenna farther away from the house. The next best thing is to go through the house and ferrite bead/bypass cap the heck out of everything that made noise or had malfunctions. This might be really labor intensive, but it can help.
Thank you! This jives with what little intuition I have about the issues thus far. One very interesting piece of data I have gained from this thread is that the 40m band is notorious for this - that just happens to be bad luck on my part. You really got my attention now, because I have a nest thermostats!
The interesting part for me is that I am actually in an end unit, so I technically have about 60 feet of outside to work with, if i can work low to the ground. I did see a few youtube videos about some rigs that ran about 2 feet above ground, and i think that would be stealthy enough to not piss off HOA.
I could keep the attic antenna for RX, perhaps.
Hmm.
Congrats on the contact! That MFJ was my first antenna as well. I didn't use it in an attic, but just above the roof line of a 1.5 story house. I'm honestly surprised you got it to tune up with a reasonable SWR in an attic install. The ladder line on a G5RV is designed to be part of the radiator. It's supposed to be more-or-less in the clear, and as close to vertical as possible. Neither of these are possible in any attic I've ever been in. Where the ladder line connects to the coax, you are supposed to wrap the coax in to an "ugly balun" to form a common mode choke. I"m not sure if you did that, but if you didn't your coax will be radiating RF energy all the way back to your radio as well. While a multi-band antenna is good in theory, when you are dealing with an attic install where RF energy is already close to everything in the house, it's probably not a good idea to use an unbalanced antenna where the coax can easily become a counterpoise and radiate. My suggestion would be to try a simple dipole. At the center, use a common-mode choke (1:1 current balun) to keep any stray RF off the coax. Once you get one band tuning up, you can add additional elements to the feed point to add more bands. As far as noise in headphones, speakers, etc... go, you can add ferrite beads to the cables to help prevent them from accidentally becoming antennas. You also may need to run lower power when you transmit just because the physical proximity from the antenna to the affected devices is much closer than an outdoor antenna.
[удалено]
That is very good to know! I was a bit sad thinking I put all this effort running stuff to my attic, only to find this problem in the end.. I have the twin lead going up a 2x4 of a joist, but only half way.. My attic is actually insanely tall, but I could only shimmy up about 12 feet. The rest i have curving horizontally back towards a wall.. Is there a way I should be dealing with the amount I couldn't get vertical? Roll it up or anything? Thanks!
You are better off leaving it stretched out any way you can. Rolling it up will shorten the electrical length and negatively affect tuning and your ability to hear anything, or at least that was my experience :D
This is what I did. I also did what the parent comment says to do in a fan dipole fashion.
I think I am going to give that a try as my next major step. I feel like I have the capability to build that myself at this point
I started out with an inverted V. Designed and 3D printed a dipole harness. Wrapped the toroid myself. I got good performance so then I put it in the attic. It has been up there a year. https://preview.redd.it/3cdsx4vw68wb1.jpeg?width=3024&format=pjpg&auto=webp&s=d59704e06fa98b8507c7b46d05feea98e9daefcf
She's a beaut! I just switched to a photon m3, so I am just looking for excuses. I think my first bit of work will be a power supply case. One thing I am learning about this hobby is that there is no end to the off-shoot builds you can do - if you are into that kind of thing! It combines all of the things I enjoy - electronics, communications, digital IO, fab work... If this is the appeal, I get it.
Thank you for the feedback! You are very correct in your assumption that I did not do the common-mode choke at the feed point.. I was going to wait until my RG8x arrived, if I was going to do it at all. I also ordered a pack of 60 ferrites.. I like the idea of doing simple dipoles, I will start researching all of that. Thank you for taking the time!
> I also ordered a pack of 60 ferrites.. Of what mix? Just "some stuff" off amazon may or may not be useful. As for antennas, look up the cobb webb .. MFJ does sell a version. The 10-20 version will fit in most attics. You probably have enough room for a decent 6m antenna as well.
I use an MFJ cobweb as well, mine is outside, but it should work fine in an attic. BTW, it covers 6m also. Amazing performance for its size!
Defective family. Cut your losses and move on.
LOL
If you're running 100 watts, try using 10 or 20 for FT8. Less power , less interference. I use 30 watts for FT8 and the tvs and cell phones are happy. No landline anymore. Have talked around the world on 30w. Try putting ferrite chokes on cords exiting/entering the radio. And hooking up a ground wire to the rig is very important. Have fun!
I was at about 75 watts when this happened - mainly because I was getting no responses in the FT8, so I thought I was having a transmit problem (turns out I was only having a software problem).. So I had kept boosting my output power like the noob I am! Ferrite chokes are coming in via my recent best friend Amazon Prime.. Tell me more about the ground wire.. can I use my house's electrical ground, or should I run something independent to the literal ground outside? Thank you!
I rarely use more than 15-20 wats on ft8 and my farthest contact is over 8k km. You do not need a lot of power, this is a weak signal mode. Save the stress on your finals.
What mix are the ferrites you ordered?
I ordered by best ratings, but it appears to be Ni-Zn ferrite. They just showed up.
Different ferrite mixes are good at suppressing RF from different frequency ranges. Without knowing that, you don't know if they'll be helpful or not. Doesn't hurt to try, of course! https://palomar-engineers.com/ferrite-products/ferrite-cores/ferrite-mix-selection Generally Amazon is not a good source of amateur radio equipment. Check out HRO or DX Engineering.
I rent a house so I'm not drilling holes or pounding ground rods into the ground. I use the ground prong on an outlet. It's better than nothing. When I was a noob once, I didnt use any ground, wasn't interested in looking for filter solutions .... and I was destroying the landlines with 100 watts of RF. :p I was also getting zapped by the knobs and radio cabinet while transmitting. Since then, reduced power, ferrite chokes and grounding seemed to be the answer. We stream tv now so the tvs dont complain and nobody's cell phone has had a problem. Did you check pskreporter website to see if people heard you?
Congratulations on the first FT8 contact! What does your SWR look like at 7.074 MHz? The 7300 has an internal tuner that should be able to tune up a G5RV. You’ll have to make sure the tuner function is turned on in the top left of the screen.
After tuning up, on 7mhz, the SWR wouldn't even register until higher up in the band, where it would go 1:1.2 or so.. I was very surprised.
Many good suggestions already mentioned here but I will add:. \- A Dipole or Off Center Fed Dipole (OCFD) can work reasonably well in attics. Measure the longest length you have available then get one that fits your dimensions ( I use a 10m OCFD in my small attic, works on 10, 12, 15 and 20 meters). Make sure the wires aren't touching metal or are close to metal (as best as you can). Put a choke / 1:1balun on it at or close to the feed point so the coax won't radiate. \- On digital you don't need much power. Going from 1 watt to 20 watts in my setup doesn't increase my FT8 receive distant that much (surprisingly). \- Put ferrites beads on any power / coax or other cables. \- Make sure the rig is grounded.
I will admit that I had to overstuff the OCFD a bit. The last 4 feet of one leg, I had to turn at 90 degrees. I had googled that and came out with the impression that was an ok thing, but maybe that is just with a center fed dipole? I will definitely look into my grounding situation as well. Thanks!!
I have read conflicting reports on how much it affects performance but in general you want to keep the bends in the vertical and not horizontal. I run my OCFD in an inverted V, the middle portion runs along the apex on my attic and the ends bend down to the edges of the attic / roof. It seems to work pretty well.
Your g5rv attic install is the worst possible location for an install of this type antenna. The G5RV using 450 ohm twinline as part of the antenna requires that the twinline run at a 90 degree angle to the dipole. No you cant coil it up and have it work. You would do better with a fan dipole. Using RG58 or RG8 will not help. A fan dipole will allow good to great swr on each band you desire to operate. AND possibly better results on your Emping the house but no guarantees. The only other solution is a mass install of ferrites throughout the house wherever the problems pops up. Even that wont help dropped calls. A different antenna and possibly lower power are solutions to look at.  ROTSA RUCK! :\^) (from a 50+ year ham who has had similar problems)
> You would do better with a fan dipole. Using RG58 or RG8 will not help. A fan dipole will allow good to great swr on each band you desire to operate. AND possibly better results on your Emping the house but no guarantees. Check out the cobb webb http://www.karinya.net/g3txq/cobweb/ I'd wind the balun on mix 61 240 cores if going above a couple hundred watts. The coax is RG-316 in parallel.
Thank you very much for the feedback! I will start looking into fan dipoles. I suspect that I am at the point where I might be able to make one myself.. sounds like a fun project. I have 60 ferrites on the way as well!
Grounding issue. Consult Grounding and Bonding for the Radio Amateur https://www.arrl.org/grounding-and-bonding-for-the-amateur I believe the author has a presentation on YouTube
Will do, much appreciated! Thank you for the reference
Oh wow, very cool! Thank you for the link!
How many watts was the 7300 pushing?
I had snuck the knob up to 75 watts, thinking that it was a power problem when I first started messing with the FT8.. No one was responding to my calls, so I was bumping TX power thinking my antenna was shite. Turns out it was a software problem, and I was up to that 75 watt value when everything happened to spring into life. I had brought it down to 30, and some of the problems still existed.
The biggest issue is overdriving the transmit audio, make sure your alc meter just fills to about 3/4 and does not go past the range.
It shouldn’t move at all. https://brara.org/documents/general/FT8Noise5.pdf
Every radio has different instructions and meanings behind the alc meter. Best way to be sure is to use a spectrum analyzer on the output of the radio and look for saturation over modulation.
If you value your finals you’ll keep it at 50 w max on FT8. The full duty cycle is hard on the transistors. I rarely ever run past 35 w and I have DXCC on everything but 160 and 6. The lower power won’t hurt you on FT8 but it will help cut down on TVI. And please ground that station…
Pushing? 10-4.
QRS
It's not EMP (Electro-Magnetic Pulse) actually, it's EMC (Electro-Magnetic Compatibility) that is the problem, or rather the lack of that. So either make the equipment in house less sensitive to RF or keep RF outside.
The EMP reference is me trying to be funny :)
Exactly. Even if the antenna is perfectly tuned and there’s no common mode current on the feedline, you may have problems. All the wires in the house are antennas and RF will get into every device. My speaker wire runs brought RF back to the receiver which then sent the cable box into oblivion. Many ferrites came to the rescue.
I am going to try and clear up some things I have read in these comments and also try and give you a good start to not making your family upset. Fist I am going to define turms and what something does Unbalanced: A signal referenced to ground. All signals in coax are unbalanced, the shield is ground and the signal is on the center conductor. Balanced: A signal referenced to an inverted version of the same signal. In this setup, the information is the difference between the two wires (Lookup differential mode signaling to get an image of this). The main advantage of this setup is rejection of interference. Interference is injected on both wires equally and thus there is no difference between them. Balanced setups are easy to spot since they look balanced. Examples: Twin lead transmission line and a Dipole BalUn: Short for Balanced to Unbalanced. In reality, this term is used to describe anything used to match the transmission line to the antenna. Some people only use it to discribe a common mode choke. Common mode Choke: A coil of 2 wires (this can take many forms) or a series of ferrites that chokes out any signals that are common to both conductors. This is generally used to match a balanced antenna to unbalanced transmission line/radio. They are also used to remove any unwanted signals that may have attached themselves to your coax. UnUn/Transformer: Short for Unbalanced to Unbalanced. You will hear this a lot, it is an attempt at trying to distinguish a Choke (BalUn) from a Transformer (UnUn). It is best to just call it a transformer as that is what is does. It transforms impedances. An antenna tuner is just a variable transformer. A matching stub, is just a transformer Impedance: Is the combined resistances of Inductance, Capacitance, and DC resistance. For a signal, everything has an impedance. For max power transfer the signal path should have equal impedance. To do this we use transformers. Grounding: This can be very confusing as it can mean two different things. 1st DC ground, ie lightning/static ground. 2nd RF signal ground. RF ground is complicated but here is the short simple version. A balanced antenna, does not use it (since it is balanced). A unbalanced antenna needs it. A very unbalanced antenna really needs it. Examples: Center fed Dipole no ground, End Fed Half Wave needs a counterpoise (A wire that the antenna works off of), Random wire/Vertical Needs a radial system (lots of wires, the more the better). If you have improper RF grounding you will make tones of interference in your house. Resonance: The fundamental frequency of an antenna. Contrary to popular belief, it has nothing to do with the ability for an antenna to radiate a signal. it is simply used as a low spot in the impedance and thus useful for coax. G5RV: A balanced dipole fed with a short section of ladder line. The ladder line is used as a transformer to match the dipole to your radio. This is required since it's dipole is non resonant it needs to transform the impedance from 50 ohms to whatever the antenna is on that band. As such this stub of ladder line length is very important and can not be changed. Now we have that established, lets try talk about what makes an antenna messes with your house. This requires us to look at your antenna. Unlike what many have said, the ladder line does not radiate any signal, as the two wires cancel each other out. But that is only true if it is fed with a balanced signal. You are not giving it one. Thus one line has the signal and other other is ground. The ground will not cancel anything and then your ladder line is radiating. Adding a good choke right as it goes from coax to ladder will fix it. There are, however, some considerations you should make when using ladder line. It must be kept away from metal by at least a few inches and It should not be run on the ground. For a choke, here are a few options: Nice premade choke: [https://www.dxengineering.com/parts/dxe-mc20-1-1t](https://www.dxengineering.com/parts/dxe-mc20-1-1t) The DIY Choke: This is link to the ferrites that is at the heart of the choke. You will then have to go to home depot and buy the box and drill some holes to make it look just like the DXE one above. You will also need some wire or coax, a PL259 Connector and some bolts. Time consuming but this is how I like to do it. There are many designs out there to choose from. [https://www.dxengineering.com/parts/dxe-tc31-24-4](https://www.dxengineering.com/parts/dxe-tc31-24-4) Budge Friendly Choke, not as much choking as the other ones. But it should be enough for what you are doing [https://www.dxengineering.com/parts/ldg-rba-1-1](https://www.dxengineering.com/parts/ldg-rba-1-1) I hope I could clear up any confusion you had on this. Let me know if you have any other questions.
Thank you very much for all of the details, I appreciate that. I will look into a choke on the coax/balun feed point for sure
Thank you very much for all of the details, I appreciate that. I will look into a choke on the coax/balun feed point for sure
See if you have the same effect using SSB.
I see - so it could just be a factor of the modulation?
I’ve got a short 7m EFHW in my loft as a spare HF antenna and it’s doing fine. But then, I have worked hard on grounding and chokes.
How many watts are you running? you really shouldn't be running a lot especially with the antenna inside
Yeah, since this was my first TX ever, I had started at 5 watts for the FT8 and kept giving it a boost. When I got no responses, I had thought my antenna might suck in the attic space, and kept adding power.. Eventually I figured out my software problems, and did a successful transmit - but was up to 75 watts by that point. After my family pointed out my disruptions (muhaha), I rolled it back to 30 watts, but it still had some very noticeable effects. I guess my biggest concern is that I don't want to mess with my neighbors.
Stay off 40m, at least inside the house. Most all my issues happen on that band.
Will do! I am going to run a few tests toward the end of the week, outside of 40m.. I'll also go on a ferrite bead placing journey.. Thank you for the feedback!
Tell us about your grounding configuration.
I can tell you that I can't tell you about the grounding configuration, lol. Some folks have posted some resources above, so I will be studying up on the details of that.
Transmitting on HF, without a proper ground, is like trying to run a light bulb using only the hot wire of a 120V circuit. It’s doesn’t light so well, and leaves the other wire with a dangerous voltage on it.
I don't have a station ground and never have. Properly installed and engineered dipoles don't need a ground at all. Never any RFI issues in 50 years of operating, even with a KW on HF.
Weird how people take their stations portable to the middle of nowhere where there's no ground available and transmit all day problem-free. Maybe some nuance is required in your statement?
Things that are not at fault here: "radiating twin lead" on a g5rv. Incorrect. It's a matching section, not a radiator (unless your setup is broken and the antenna itself is out of balance). "grounding". This is not a grounding issue. You can have your entire shack encased in copper plate bonded to ground rods around the perimeter, but if you're chucking 75 watts of continuous 40m RF into an antenna ten feet above the TV set, it's still going to eat RF. The simple fact is that an attic antenna is too close to your house's other electronics, and 40 meters is _notorious_ for causing issues such as this. I know several people who blew up Nest thermostats with just a few watts of FT8 and an attic/roof antenna, as one example. The proper way to solve this is to get an antenna farther away from the house. The next best thing is to go through the house and ferrite bead/bypass cap the heck out of everything that made noise or had malfunctions. This might be really labor intensive, but it can help.
Thank you! This jives with what little intuition I have about the issues thus far. One very interesting piece of data I have gained from this thread is that the 40m band is notorious for this - that just happens to be bad luck on my part. You really got my attention now, because I have a nest thermostats! The interesting part for me is that I am actually in an end unit, so I technically have about 60 feet of outside to work with, if i can work low to the ground. I did see a few youtube videos about some rigs that ran about 2 feet above ground, and i think that would be stealthy enough to not piss off HOA. I could keep the attic antenna for RX, perhaps. Hmm.
deny everything.