the house hummmmsss

rjvalenta

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got my general about a month ago... put a 4010 EFHW on the peak of my slate roof running out into a tree in the back yard... about 10ft of the antenna is above the slate roof that kept me from using antennas in my attic or a metal overhang... the rest of the wire is over the yard sloping upwards from about 15' up at roof peak to 20' up in the tree. i did not add any kind of counterpoise at the balun.

abr coax into the house where it meets an MFJ RF filter, then into my MFJ939i tuner, then into the IC7100. all this is in the attic... then a shielded cat6 cable runs across the attic and down a hole into the wall and on to my desk where the control head is. everything has some kind of ground.

so far, 800+ QSO's, 620+ confirmations in 108 countries - all FT8 or FT4.

not proficient with CW, and not ready for phone yet, though i like to get on DXSummit and chase the conversations.

BUT - here's the real issue:

if i use 20m or 10m everything is fine.

if i use anything else from 80m, 40m, 30m, 17m, 15m, or 12m the house starts to hum... more on 40m and 17m, but always some hum, sometimes lights will flicker, and on 40m (sometimes 80m and 30m) i will knock the house off the internet briefly... just long enough to knock people out of their video games.

and boy do i hear about it.

the internet is from the cable company, but the tv's don't get distorted... but the hum from the computer speakers or other speakers makes me feel like i'm frying myself, or at the very least i'm doing something wrong.

i would think the 1:1 current balun rf isolator would keep things from causing interference in the house... and i would think the roof i couldn't get good reception through would keep the EFHW from causing RFI inside... and generally i'm not pushing power (as i'm typing this i have the radio set for 40w).

for weeks i assumed this was just the nature of the beast, but then today i watched a video of K8MRD replacing his coax and noticed that he has a dipole running the length of his house, right down the middle, just feet off from the peak... like he just reached up to the feed point and changed out the coax... and so many other videos where guys have antennas all over their roofs... are they all getting a hum throughout their house on everything but 20m and 10m?? are they all losing their internet connection when they talk on 40m?

or... is this a problem with my tuner... or would it be resolved if i had a counterpoise... or do i need to add ferrite cores to every wire in my house... or....

suggestions anyone?

thanks,

Richard
N0TZC
 

TexTAC

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I had similar issues with my OCFD antenna when I first installed it. Four things eliminated it. (1) moving the antenna further away from house. (2) moving the antenna cable further away from where the TV/internet cable entered the house. (3) using an RFI isolator like the MFJ-915. And (4) using a good tuner to improve SWR. I was knocking out our internet and causing the stereo speakers to hum loudly before those items solved the problem. Good luck!
 

popnokick

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abr coax into the house where it meets an MFJ RF filter, then into my MFJ939i tuner, then into the IC7100. all this is in the attic... then a shielded cat6 cable runs across the attic and down a hole into the wall and on to my desk where the control head is. everything has some kind of ground.
What MFJ filter? You may want to replace that with a Palomar or similar 1:1 unun. And I'm assuming the "filter" is on the antenna side of any tuner or antenna switch. I have a 7100 with two different antennas on an A / B switch and a Palomar 1:1 AFTER the switch (on the transceiver side). I was still getting RF into the shack and it was killing my computers. I tried several different toroids... both snap-on and wrap-around mix31 ring... and no joy. Then I thought "Maybe the unun should be the first thing before the switch and tuner". I moved the unun and Voila! Problem solved. My unun is a Palomar Mini-Choker
 

MUTNAV

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This wont help solve your problem, but just letting you know I love the mad scientist aspect of having the lights flicker while you're working on your hobby.

Get some sparks to fly around the kitchen once in awhile and you'll be set.
:)
Thanks
Joel
 
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Richard, I think you have all sorts of RF radiating back into your house.
I am not a big fan of these off-centre feed antennas, especially if there is no counterpoise. Common mode currents running back down your feedline is just one of my issues with them--

Yes, you can try to choke them out with various filtering schemes, but that's just putting a band-aid on the problem

I would suggest at a minimum attaching a counterpoise.

I am, however, a fan of TLW (Terminated Long Wires)--- these are non resonant antennas that terminate in a high value (600-1000 Ohms) resistor of appropriate wattage. They are basically what you have with a resistor at the end terminating in a counter poise wire or a ground. I have used them for many years in all sorts of environments and never had any issue like you are experiencing---
Without a tuner you should have a near 1:1 SWR-- another plus.

TLW's can be a single wire like yours, or fold'd back and made into a folded dipole (my favorite.)

The down side is that these antennas will have an immediate 3dB loss over conventional dipoles, but, Hey--- if you can't operate without tearing things up in your house hold --------

If you can get a 600 to 1000 Ohm resistor of 50-100 watts (you say you are running QRP) -- it would definitely give this a shot.
It will be a compromise, but what in life isn't to some degree :) ??


Lauri

.
 
Last edited:

popnokick

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got my general about a month ago... put a 4010 EFHW on the peak of my slate roof running out into a tree in the back yard.
Richard - quoted the above to clarify that you have an End-Fed Halfwave (EFHW) not an Off-Center Fed Dipole (OCFD).

The EFHW antennas from MyAntennas (and many others) have a place to attach a counterpoise wire. Our club has two of them and we have never had to use a counterpoise. However, it might be a simple fix for you since you write that you do not have a counterpoise. Some EFHW setups work better with one. You'll find the place to attach the counterpoise is likely a wing nut on the balun / unun where the coax is attached to the end of the radiating element. You wrote that your antenna is up 15 feet at the feed end, so attach 15-20 feet of 18 to 14 gauge wire. Use wire that is flexible enough that it will hang down away from the radiating element / balun. Position is not critical... you could drape it across the roof if need be. Leave that far end of the counterpoise wire unterminated and ungrounded... just hangin' there. If it doesn't work... well, you're out a 20 foot piece of wire and a little of your time to attach it.
 

rjvalenta

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Richard - quoted the above to clarify that you have an End-Fed Halfwave (EFHW) not an Off-Center Fed Dipole (OCFD).

The EFHW antennas from MyAntennas (and many others) have a place to attach a counterpoise wire. Our club has two of them and we have never had to use a counterpoise. However, it might be a simple fix for you since you write that you do not have a counterpoise. Some EFHW setups work better with one. You'll find the place to attach the counterpoise is likely a wing nut on the balun / unun where the coax is attached to the end of the radiating element. You wrote that your antenna is up 15 feet at the feed end, so attach 15-20 feet of 18 to 14 gauge wire. Use wire that is flexible enough that it will hang down away from the radiating element / balun. Position is not critical... you could drape it across the roof if need be. Leave that far end of the counterpoise wire unterminated and ungrounded... just hangin' there. If it doesn't work... well, you're out a 20 foot piece of wire and a little of your time to attach it.

i was just emailing someone about the counterpoise idea... everything is on the roof, adding the wire to the counterpoise point on the transformer will be a much easier while i consider and try to understand everything Lauri said. so. much. to. learn.

thanks all! any other ideas will be entertained or researched!
 

G7RUX

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Jul 14, 2021
Messages
362
got my general about a month ago... put a 4010 EFHW on the peak of my slate roof running out into a tree in the back yard... about 10ft of the antenna is above the slate roof that kept me from using antennas in my attic or a metal overhang... the rest of the wire is over the yard sloping upwards from about 15' up at roof peak to 20' up in the tree. i did not add any kind of counterpoise at the balun.

abr coax into the house where it meets an MFJ RF filter, then into my MFJ939i tuner, then into the IC7100. all this is in the attic... then a shielded cat6 cable runs across the attic and down a hole into the wall and on to my desk where the control head is. everything has some kind of ground.

so far, 800+ QSO's, 620+ confirmations in 108 countries - all FT8 or FT4.

not proficient with CW, and not ready for phone yet, though i like to get on DXSummit and chase the conversations.

BUT - here's the real issue:

if i use 20m or 10m everything is fine.

if i use anything else from 80m, 40m, 30m, 17m, 15m, or 12m the house starts to hum... more on 40m and 17m, but always some hum, sometimes lights will flicker, and on 40m (sometimes 80m and 30m) i will knock the house off the internet briefly... just long enough to knock people out of their video games.

and boy do i hear about it.

the internet is from the cable company, but the tv's don't get distorted... but the hum from the computer speakers or other speakers makes me feel like i'm frying myself, or at the very least i'm doing something wrong.

i would think the 1:1 current balun rf isolator would keep things from causing interference in the house... and i would think the roof i couldn't get good reception through would keep the EFHW from causing RFI inside... and generally i'm not pushing power (as i'm typing this i have the radio set for 40w).

for weeks i assumed this was just the nature of the beast, but then today i watched a video of K8MRD replacing his coax and noticed that he has a dipole running the length of his house, right down the middle, just feet off from the peak... like he just reached up to the feed point and changed out the coax... and so many other videos where guys have antennas all over their roofs... are they all getting a hum throughout their house on everything but 20m and 10m?? are they all losing their internet connection when they talk on 40m?

or... is this a problem with my tuner... or would it be resolved if i had a counterpoise... or do i need to add ferrite cores to every wire in my house... or....

suggestions anyone?

thanks,

RichardC
To be honest, the antenna is likely too close to stuff in the house and may require moving away a little. That said, an EF antenna with no counterpoise will result in the coaxial feeder screen being the counterpoise and bringing RF into close proximity with stuff in the house. Adding a counterpoise will likely improve this quite markedly.
 
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Messages
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.
Richard---

Like I was saying, I am proponent of terminated antennas. Here is probably more information than is reasonable about them, but reading thru it could plant a few ideas ;)



Lauri

.

T2FD_Antenna_2.png



images.png
 
Last edited:

G7RUX

Member
Joined
Jul 14, 2021
Messages
362
.
Richard---

Like I was saying, I am proponent of terminated antennas. Here is probably more information than is reasonable about them, but reading thru it could plant a few ideas ;)



Lauri

.

View attachment 142665



View attachment 142667
The T2FD is a favourite of mine since I really like travelling wave antennas (and I don't have space for a rhombic!) and its performance is pretty good. Yes, yuo lose some output power in the termination resistor but if the length of the antenna is decently close to a half wave for the lowest frequency you want to use then it can be reasonably efficient. Similarly, you will lose a bit of the received signal too but it's not huge. However, and here is the big advantage with the T2FD and antennas like it...you don't need a tuner!
 

db_gain

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Joined
Sep 13, 2014
Messages
100
Put ferrites or a ferrite ring with as many turns of line as possible at each end of any given line, be it coax or cat5.
Put ferrites on all pc cables too. Also bundling all cables together, radio, pc, whatever, sometimes changes things, for better or worse.
Also a inexpensive hf lowpass filter that goes inline with the coax can make a difference in some situations, and will ensure nothing gets out harmonics-wise from your rig. You can find hf lowpass filters at most any HAM vendor.
 
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