Topics

Close Proximity

Ken Campbell
 

Hi all,
I’m wondering if any of you  have had issues with antenna  close proximity? I run an ic-7300 on HF and have my ic-7000 set up to use mostly on VHF/UHF. My antennas are quite close to each other as we live in a townhouse, less than 10 feet apart. Normally I don’t run both radios simultaneously. If I were to do that, does anyone think that could be a problem, as in doing damage to either radio? Would really appreciate your thoughts on this. Thanks! :-)

All the best,
Ken N6PCD

Helmut Wabnig <hwabnig@...>
 

On Fri, 23 Aug 2019 08:21:56 -0700, you wrote:

Hi all,
I’m wondering if any of you  have had issues with antenna  close proximity? I run an ic-7300 on HF and have my ic-7000 set up to use mostly on VHF/UHF. My antennas are quite close to each other as we live in a townhouse, less than 10 feet apart. Normally I don’t run both radios simultaneously. If I were to do that, does anyone think that could be a problem, as in doing damage to either radio? Would really appreciate your thoughts on this. Thanks! :-)

All the best,
Ken N6PCD
Although I should have known better, I destroyed two LED lamps,
one 2 meter amateur transceiver inclusive its power supply,
and one laptop computer with all the software on it.

By transmitting in near proximity.

OE8UWW

Den W2DEN
 

You can damage a receiver's front end, and more, with high levels of RF. I am not an expert on RF levels but something to keep in mind.
From Field Day and contesting experience you may want to look into band pass filters if you intend on operating two HF radios in close proximity.
73 Den

Paul Hansen
 

Ken,

              I repair 3 or 4 radios per week that have been damaged from RF overload. Most are HF radios. VHF and UHF radios are not immune. What’s worse, the radios do not have to be turned on to be damaged. RF will damage the small switching and amplifier components regardless of being energized. Your VHF installation is very much like many marine installations I repair. Larger charter boats like to have redundant VHF radios. The antennas are frequently mounted on stanchions or rails around the flying bridge. Separation is often less than 15 feet. The first FET RF amplifier gets damaged and receiver sensitivity decreases by about 20db. The only way to prevent this from happening is either removing the antenna from the least used radio or installing a lock out relay.

              HF radios are similarly damaged but the antenna separation distances can be much greater. A pair of verticals separated by 100 feet can be mutually destructive if a linear amplifier is involved. Normally, RF overload damage in HF radios is much more expensive to repair because the RF takes out TX/RX switching, band pass filter selection diodes, attenuator resistors, and small RF amplifiers (even transmit amplifiers). Again, turning the radio off isn’t going to do the job. The antenna has to be grounded or disconnected.

              Here’s another thing I see all the time. You have an IC-7000 set up to run HF through 6 meters on an antenna system. Then you have a nice 2 meter gain antenna mounted on top of your HF antenna or right next to it. What could be wrong with that? HF won’t bother your VHF receiver, will it? Because your IC-7000 has an antenna connector for HF through 6 and one for VHF and UHF an odd problem crops up. You run a bunch of summer sporadic E on 6 meters. Then you find your 2 meter receiver is not working well any longer. Why? The third harmonic of 6 meters is right in the pass band of the 2 meter front end and it has enough energy to cause damage to it. As far as RF energy is concerned, three times six equals two. I see a couple of these per month.

              I hope that covers what you want to know. Disconnect your unused radios until you can develop a lock out switching system. A manual grounding antenna switch is ok but it relies on you remembering to use it. If you run power on HF, a typical non-grounding antenna switch isn’t good enough.

 

Thank You

 

Paul W. Hansen, W6XA

Amateur Radio Service

2134 Carthage Road

Tucker, GA 30084

(864) 222-3539

www.amateurradioservice.com

 

From: ic7000@groups.io [mailto:ic7000@groups.io] On Behalf Of Ken Campbell
Sent: Friday, August 23, 2019 11:22 AM
To: ic7000@groups.io
Subject: [ic7000] Close Proximity

 

Hi all,
I’m wondering if any of you  have had issues with antenna  close proximity? I run an ic-7300 on HF and have my ic-7000 set up to use mostly on VHF/UHF. My antennas are quite close to each other as we live in a townhouse, less than 10 feet apart. Normally I don’t run both radios simultaneously. If I were to do that, does anyone think that could be a problem, as in doing damage to either radio? Would really appreciate your thoughts on this. Thanks! :-)

All the best,
Ken N6PCD

D C *Mac* Macdonald
 

I consider it mandatory for EVERY transmitter at a Field Day site use the appropriate bandpass filter at all times.  Mr Sherwood will tell you that almost every transmitter or transceiver has broadband noise coming out of it.  At our Field Day operation this year, there was a brand new transceiver that put out wipeout level noise on 20, 15, and 10 meters whenever it was keyed up on 6m SSB even without any modulation!
 
73 de Mac, K2GKK/5​
Since 30 Nov 1953​
Oklahoma City, OK​
USAF, Retired ('61-'81)​
FAA, Retired ('94-'10)​
 

W8RMV
 
Edited

If you have an external wattmeter, hook it up to the coax of the unused antenna system & transmit into the other antenna system.  You might be amazed by how my power goes into the unused antenna system and therefore into the passive transceiver.  I know I was.
- Bob W8RMV