VHF Issue
On a recent trip up North I found out my VHF would only work within say 3nm ish. It used to work fine, could talk to Geraldton sea rescue from the Abrolhos no issues.
As it was a cheap GME setup d ~5yrs old I replaced the VHF and antenna with a new ICOM VHF and Pacific 2.4m 5db antenna.
However I am having the same issue with the new setup, VHF only works up to say 3nm. I am thinking there is 3 possible causes but any tips for narrowing down the cause would be appreciated.
1 - Dodgy power connection to VHF unit so that it isn't getting enough power. Visually checked the wiring, there was a slightly dodgy connection which I have fixed but haven't had a chance to test since. Not sure if this would reduce the receive ability (we had the VHF on all day at direction bank, monitoring 16 & 73 and heard nothing).
2 - Dodgy fitting the antenna plug. The pacific antenna came with the plug not fitted so the cable could be cut to length. I followed the instructions and thought I fitted it correctly but maybe not?
3 - Faulty antenna or VHF. Probably unlikely but I have been caught a few times before with faulty new products so can't disregard.
Any tips?
groverwa
Posts: 286
Date Joined: 21/07/14
faulty coax lead
It could be a faulty coax lead but without the proper test equip you could try renewing that coax or try your unit in someone elses boat. The coax may look ok but if what is known as the characteristic impedance does not match the antenna and the radio unit then the transmitted power from the VHF unit can be reflected back into itself and give the reults that you have indicated.
The coax for radios must be 50 ohm and for TVs must be 75 ohm. Wrong impedance cable will give what I have described above.
Your local sea rescue may have the test equip - a suitable dummy load and power meter - to analyse any problems.
Rig
Posts: 2925
Date Joined: 27/12/06
VHF
I have had poor performance before and re-terminating the antenna lead has fixed it, sometimes if 1 little strand of the coaxial sheath gets through poor termination which can be hard to see if your not familiar with these types of cables it will do this
Also if its the pacific antenna that screw in make sure its screwed in the whole way as you may have a poor or corrded connection on the antenna base, but just take it off and check it again put some vasoline on it also
z00m
Posts: 1086
Date Joined: 10/05/14
Process of elimination
You've replaced the radio and the antenna.
If you didn't replace the base and lead for the antenna then that is the likely culprit.
If you did then the power wiring would be the next step. This is unlikely to affect Rx, mainly only affects Tx. You say you didn't hear much on direction bank but that could be as much about who was out where on that given day. If you can't contact sea rescue within 10nm of the coast then for sure a problem.
Have you changed/installed anything else on the boat before you had the original problem?
Silly question, you aren't trying to contact sea rescue on the low power setting? 1w low power setting vs 25w high power.
Taffy
Posts: 183
Date Joined: 04/11/10
Like Zoom Said
Like Zoom said, do you have it set on High power ??
VaSSagO
Posts: 126
Date Joined: 09/12/09
Thanks for the input
Thanks for the input guys.
Yes was definitely on high power (25w) and the base & coax cable was replaced.
I think I will check to see the antenna is plugged into the lead at the base correctly and then see if can test the impedance on the antenna / lead, if not ~ 50ohm I will cut-off the plug at the end of the cable and try to refit correctly. Fingers crossed this is the issue.
ranmar850
Posts: 2702
Date Joined: 12/08/12
Also check your power
You can have 12.4 volts there by your mulitmeter, but, if you have a high resistance joint or power cable/fuse which has seen better days, that will reduce your transmit power significantly.