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Author Topic: Receive issue-in rig or antenna system?  (Read 871 times)
AF5CC
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« on: March 24, 2013, 11:54:51 AM »

I have an Icom 706 original which I have owned for the past 2 years and really like (other than the NB not being that good on consumer electrical noise).  I have noticed for the past few months that the receive seems to drop at times on certain bands-it started on 12m and now occurs on 15m as well, and has started to show up on other bands, like 17m and 30m for the first time last night. If  you click the key or mic to quickly put it into transmit the receive comes back.   To me this sounds like a dirty relay or one that is going bad. 

Someone did suggest to me that it could be a problem in the antenna system as well. I did some checking this morning, and have determined that it isn't in the low pass filter, the MFJ tuner, or any jumper coaxes in the shack.  It would have to be in the feedline going to the G5RV, or the balun there.  I haven't had time to change out the coax run yet.  Would an antenna problem affect some bands more than others?  I use the same antenna and feedline for all HF bands.

I have also noticed that on 12m and 15m the receive will come back up by itself at times.  Sometimes it is a quick drop down and come back several times in succession.  Would a relay problem do this?

So, with this latest information, what is the better guess as to the problem-in the rig or the antenna system?

73 John AF5CC
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NO2A
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« Reply #1 on: March 24, 2013, 03:24:03 PM »

Sounds like the relay is sticking. I wouldn`t suspect the antenna unless your swr suddenly goes skyhigh.
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W8JX
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« Reply #2 on: March 24, 2013, 03:54:47 PM »

Sounds like the relay is sticking. I wouldn`t suspect the antenna unless your swr suddenly goes skyhigh.

I agree if SWR is stable but it is also possible there is a loose connection in antenna circuit that is fine when transmitting but intermittent at micro volt signal levels. 
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NO2A
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« Reply #3 on: March 24, 2013, 04:36:12 PM »

The reason I believe it`s the relay is because he said when he keys the mic or key,the receive comes back. The relay in my rig acts up at times,but only if I`m driving my amp. Mine is the same way,if I tap the key the receive comes back.
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AF5CC
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« Reply #4 on: March 24, 2013, 04:38:56 PM »

However it does come back on its own at times, without keying the paddles or mic.  Sometimes, mostly on 12m, it will cycle between low receive and normal receive a few times on its own. If it is a coax connector problem, would it only show up on certain bands?

John AF5CC
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NO2A
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« Reply #5 on: March 24, 2013, 04:57:58 PM »

A bad connection would affect all bands you use with that antenna and coax. If you have a dummy load you could try that. I`m willing to bet it`s the relay. Maybe you have another rig you could connect with that antenna. I still bet it`s the relay.
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W8JX
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« Reply #6 on: March 24, 2013, 05:17:58 PM »

A bad connection would affect all bands you use with that antenna and coax. If you have a dummy load you could try that. I`m willing to bet it`s the relay. Maybe you have another rig you could connect with that antenna. I still bet it`s the relay.

Not always. It could indeed be frequency depend at times. My first choice here is a relay as you stated but it is possible to be external.
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AF5CC
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« Reply #7 on: March 25, 2013, 12:15:51 PM »

It does appear to be in the radio. I tried the tapping on the case method with no luck, but when the receive level dropped on 12m, I switched over to my 6 meter beam, since it uses a different feedline.  I keyed the rig quickly.  When I switched back to the dipole the receive level was back.  Since it was keyed on a different feedline, it doesn't appear to be in the antenna system. 

73 John AF5CC
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M6GOM
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« Reply #8 on: March 26, 2013, 03:42:15 PM »

It could be in the antenna system. Corrosion in a connection behaves like this.
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