topbuzzuk
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RF feedback? i'm not sure?
right... when i switch the burner on at home with a power mic connected i get a carrier on ssb, if i turn the mic right down(nearly off)it disapears. If i use a standard mic this doesnt happen. what could be the problem?
the antenna is in the loft above the room i have the radio in and the coax runs along the loft floor for about 5 foot(horizontal)then out through the hatch down to the room. I have had a simular problem when tryin out a radio with a magmount in the same room. If anyone can give me a list of things to try i would be gratefull, i've read somewhere it might be cos there is not enough groundplane on the antenna or bad earths or summit, help would be apreciated, or a check list i can start doing to narrow it down. i have read a bit on the internet but get a bit lost with words like counterpoise???? help
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26FB118 ~~~ 26PR13
Home:Icom 706MK2G-Heil HMM-IC mic-Inverted V ant(indoor)
Mobile:Ranger VR9000-Astatic Teardrop mic-Zetagi B300P amp-Moonraker SC5000 ant
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6/Feb/2008, 11:43 pm
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yamanx1
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Re: RF feedback? i'm not sure?
Sounds like it could be a few things.
I would, check the mic wiring, particularly make sure no possible contact between pins.
Try with head phones.
The power mic will cause the linear to actually put out a higher average pep, increasing your power up that coax, so your assumption about rf feedback could be right, coming from your coax, a method of eliminating this, without changing all your coax to expensive RG213 is an rf choke.
What you need to do is coil around 8-10 feet (for 11m only for all other bands as well you'll need 18-21 feet)of coax around a plastic pipe. Making sure all the coil touch but the last one doesnt touch the first. Normally you would place this near the mast as a balun (Balances unbalanced coax with balanced aerial) but in your case I would do it straight out the back of the radio.
More information here RF Choke/Balun
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7/Feb/2008, 12:29 pm
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topbuzzuk
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Re: RF feedback? i'm not sure?
all sorted thanks to the balun, ive got rid of the carrier on ssb with the mic on full and the burner going. i havnt had any on air reports as yet but i think its done, thanks Dave
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26FB118 ~~~ 26PR13
Home:Icom 706MK2G-Heil HMM-IC mic-Inverted V ant(indoor)
Mobile:Ranger VR9000-Astatic Teardrop mic-Zetagi B300P amp-Moonraker SC5000 ant
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9/Feb/2008, 1:05 pm
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topbuzzuk
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Re: RF feedback? i'm not sure?
well i just put the astatic in the discovery on the ranger and i had the same problem as i did in the homebase, i have cured the problem but have never heard of this before. i wound the mic cable(plug end)twice around a ferrite choke and hey presto no more carrier on ssb with the power mic. i wonder if that may have worked on the homebase???
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26FB118 ~~~ 26PR13
Home:Icom 706MK2G-Heil HMM-IC mic-Inverted V ant(indoor)
Mobile:Ranger VR9000-Astatic Teardrop mic-Zetagi B300P amp-Moonraker SC5000 ant
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24/Feb/2008, 9:05 pm
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