How can i test my mast mounted VHF antenna
- Thread starter emergpa1
- Start date
You can't.
A VHF antenna will show its 50ohm resistance only at VHF operation frequencies. A regular ohm meter will show open or closed depending on antenna design. You need a SWR meter. Borrow it, or they run about 50 bucks.
A VHF antenna will show its 50ohm resistance only at VHF operation frequencies. A regular ohm meter will show open or closed depending on antenna design. You need a SWR meter. Borrow it, or they run about 50 bucks.
Get on the radio and do a radio check? This will give you a go idea if you are transmitting and receiving. Although there might not be too many boats monitoring the radio this time of year, depending upon where you are. If your mast is down this might not work out too well either, Steve.
How can I test my VHF antenna?
Rather than relying on other boaters to do a radio check, use this free automated radio check service. http://www.seatow.com/boating-safety/automated-radio-checks
What about the SWR Meter/Tester from Shakespeare?
http://www.amazon.com/Antenna-Radio-Tester-Tx-Rx/dp/B000OTJAOE
http://www.amazon.com/Antenna-Radio-Tester-Tx-Rx/dp/B000OTJAOE
Although I've never tried this, it could be a reasonably priced method if you can fond a cheap CB SWR meter.
http://www.kb6nu.com/no-vhf-swr-meter-no-problem/
If you were in this area, i would do it for you.
http://www.kb6nu.com/no-vhf-swr-meter-no-problem/
If you were in this area, i would do it for you.
CB Radio SWR meter will not work. That meter works in the 27 MHz band. You will need a meter for the 150 MHz band.
An SWR meter will not tell you if your system is working right. Yes, it will test the entire system for continuity and resonance, meaning that you will have minimal power lost to the antenna. But it will not test how well the antenna is radiating.
You will need to do just about all of the above to really determine if you are doing well.
Check the SWR to make sure you are not losing too much power from the radio. Here is a SWR power loss chart based on 4 watts. http://www.firestik.com/Tech_Docs/SWRLOSS.htm You will see that at an SWR of 2:1 you will lost 11% of your power.
Use the BoatUS repeater discussed above. That will test your audio. You will be able to tell if you are transmitting noise with your signal, including static (dirty mic contacts?). You will hear your own signal.
Stay off Channel 16 for radio checks. Listen on 22, 68, or other channels for other boaters. Ask them for a radio check and get there approximate location to determine your range.
Do all the above to really determine if you system is working well.
An SWR meter will not tell you if your system is working right. Yes, it will test the entire system for continuity and resonance, meaning that you will have minimal power lost to the antenna. But it will not test how well the antenna is radiating.
You will need to do just about all of the above to really determine if you are doing well.
Check the SWR to make sure you are not losing too much power from the radio. Here is a SWR power loss chart based on 4 watts. http://www.firestik.com/Tech_Docs/SWRLOSS.htm You will see that at an SWR of 2:1 you will lost 11% of your power.
Use the BoatUS repeater discussed above. That will test your audio. You will be able to tell if you are transmitting noise with your signal, including static (dirty mic contacts?). You will hear your own signal.
Stay off Channel 16 for radio checks. Listen on 22, 68, or other channels for other boaters. Ask them for a radio check and get there approximate location to determine your range.
Do all the above to really determine if you system is working well.
The proof is in the pudding, get on the radio and solicit a radio check. Don't just rely on a nearby boat but try to establish communication 10+ miles.
Get your wife or teenage daughter to do the radio check. I'm very sure they will get ten times the response if it is done by you. And may be as far away as 100 miles! Just kidding...
The SeaTow automated system mentioned by Ted is better than a SWR meter as it will retransmit your call so that you can hear the voice quality. This can uncover problems with your mike, electrical noise, or frequency problems. The location of the antenna is on their web site so you can also get an accurate range.
The checks are on channels 24,26,27, or 28. Just try each one until you get the automated response.
And thank you for not adding to the "radio check" chatter on channel 16
The checks are on channels 24,26,27, or 28. Just try each one until you get the automated response.
And thank you for not adding to the "radio check" chatter on channel 16
Actually the receive function will tell as much about your antenna as the transmitter. The most practical way to check it is just tune in a distant station such as a weather station. This will only check one frequency but if your antenna was ever set up properly that should be enough to identify a problem. A VSWR check is absolutely the right answer, but if you don't have one it could be a bit costly. Someone above indicated a CB radio VSWR meter won't work. That depends on the type of VSWR meter. The cheaper ones aren't a problem. I've used the one I have with good success on everything from HF to UHF.
An antenna radiation pattern problem won't be identified here, but assuming good VSWR it would be a difficult to imagine a problem like that with a simple loaded dipole.
Bottom line, with over 40 years of commercial electronics experience I've found if your boat next door can receive a weak weather station with about the same noise as you, your antenna system is most likely fine (assuming the other boat is fine.)
Here is the same model of meter I've had so much success with. it's cheap ($10 used) and really simple.
http://www.ebay.com/itm/VSWR-Field-...3?pt=US_Radio_Comm_Meters&hash=item2a37674739
Ken
An antenna radiation pattern problem won't be identified here, but assuming good VSWR it would be a difficult to imagine a problem like that with a simple loaded dipole.
Bottom line, with over 40 years of commercial electronics experience I've found if your boat next door can receive a weak weather station with about the same noise as you, your antenna system is most likely fine (assuming the other boat is fine.)
Here is the same model of meter I've had so much success with. it's cheap ($10 used) and really simple.
http://www.ebay.com/itm/VSWR-Field-...3?pt=US_Radio_Comm_Meters&hash=item2a37674739
Ken
Receive and transmit are TOTALT different. You can receive on just about anything. You can only transmit on a resonant antenna. Your AM car radio is a great example. If you tried to get an AM signal out on that little thing it would fry your transmitter but you can receive on it fine. You would need an antenna that was something significantly longer than 160 meters to get out a signal on those AM frequencies.
And yea I do understand that there are shorter antennas that can be constructed but lets limit ourselves to "typical" wip antennas with only inductors at the base like are common on VHF marine radios.
Best bet is the acid test, make a radio check and get their location. Then it is not a theory it is an established fact.
And yea I do understand that there are shorter antennas that can be constructed but lets limit ourselves to "typical" wip antennas with only inductors at the base like are common on VHF marine radios.
Best bet is the acid test, make a radio check and get their location. Then it is not a theory it is an established fact.
Here is a sneaky trick, but I personally would not try it. I live and boat between L.A. and San Diego. I hear both USCG Stations broadcasting PANs. If I want to see if I could talk that far, I would ask for addition information from the station. But like I said, I personally would not do it.
Sorry Bill Rosa
I suspect most folks won't want this detail but since you brought it up:
Receive and transmit are actually opposites in the direction of signal flow but both depend equally on the characteristic impedance where the signal won't travel through a mismatch. In the case of a VHF radio the receive and transmit must both be tuned to a 52 ohm impedance. Any variation will reduce signal flow. That's why I specified listening to a marginal signal. It's true of any transceiver that shares the same antenna for receive and transmit.
This is a common design characteristic. Here is a pretty good primer:
http://www.maximintegrated.com/app-notes/index.mvp/id/742
I have seen this many times over the years. and it's pretty easy to demonstrate.
The reason we are more picky about transmitter VSWR is because it can result in an overheat and cause damage to the transmitter, where a receiver simply degrades in sensitivity.
Ken
I suspect most folks won't want this detail but since you brought it up:
Receive and transmit are actually opposites in the direction of signal flow but both depend equally on the characteristic impedance where the signal won't travel through a mismatch. In the case of a VHF radio the receive and transmit must both be tuned to a 52 ohm impedance. Any variation will reduce signal flow. That's why I specified listening to a marginal signal. It's true of any transceiver that shares the same antenna for receive and transmit.
This is a common design characteristic. Here is a pretty good primer:
http://www.maximintegrated.com/app-notes/index.mvp/id/742
I have seen this many times over the years. and it's pretty easy to demonstrate.
The reason we are more picky about transmitter VSWR is because it can result in an overheat and cause damage to the transmitter, where a receiver simply degrades in sensitivity.
Ken