gaffa Posted April 15, 2015 Report Share Posted April 15, 2015 Was out yesterday and received a friendly call on the VHF from plaicemat so pressed the transmit and replied as you do but he couldn't receive the response which was pretty serious as he was only about 100m away. Anyway to cut a long story short I fixed the problem today prior to going out again it took about an hour overall. And lesson learn't get a radio check before leaving on every trip I suspected the problem was aerial based so got the ohmeter out and sure enough there was a short circuit between the inner connector pin and the outer casing(screen) There is a lot of misinformation on the net and one site stated that there should be an open circuit between the coax inner and screen and that a short circuit indicates a fault...Be carefull it could be a great way of beefing up his aerial sales but could also be valid on aerials without ground planes so you need to know which type of aerial you have. Mine definitely had a ground plane. The fibre glass aerial is simply a shroud covering a loop of wire with the coax inner soldered to one side of the loop and the screen/braid to the other side of the loop so at dc (0 hz) the metal loop short circuits the cable connections. However at its tuned radio frequency (156-162Mhz) it is no longer a short circuit as it has inductance and capacitance which is frequency related and exhibits an impedance of around 50 ohms which allows the transmitter to function. So to fix the problem I made the assumption that the cable connections needed re-soldering and the coax braid redressed in the connector so it made a firm connection and did not touch the inner. To make sure I got this right I un-soldered the coax inner connection from the loop (needed to slide the fibreglass forward a couple of feet to get access) and made sure it couldn't touch it or the braid connection By doing this i could ensure i was not shorting out at the connector and when happy i re-soldered the connection on the loop and reassembled the lot. I got a radio check with the marina to ensure i was transmitting and then another when i got to around the end of the Swash at Old Harry and the received transmission at this distance was a little crackly which I could imagine was due to poor aerial performance....The coax cable is dated 1996 so maybe the aerial is too. I think it maybe time I invested in a new one Stuie and charlieannear 2 Quote Link to comment Share on other sites More sharing options...
Brian Posted April 16, 2015 Report Share Posted April 16, 2015 As an addition to this. I have a professional VSWR meter, if any member needs to check their aerial. Quote Link to comment Share on other sites More sharing options...
Coddy Posted April 16, 2015 Report Share Posted April 16, 2015 10 4 Good Buddy!! Quote Link to comment Share on other sites More sharing options...
Brian Posted April 16, 2015 Report Share Posted April 16, 2015 10 4 Good Buddy!!It's not for CB frequencies (although I have got those as well). Off for a 10-100, so 10-50 catch you on the flip flop. gaffa, Jim and Coddy 3 Quote Link to comment Share on other sites More sharing options...
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