Well, it seems that I have now solved half the problem. I bought a Yaesu 850 and I am told that my readability is 5 even at 10km. The old radio stopped transmitting completely so what I suspect is that the output stage was failing gradually over the past few years.
Reception remains poor, I think because of noise from the mags.
Yes, you do have to have the other half of the antenna too (with a handheld, you are the counterpoise). I usually mount a connector on a baking sheet to use for testing/tuning VHF/UHF whips.
Thanks for putting it in context.
I suppose the other possibility is that I don’t know how to test the antenna correctly, or that it only works well when attached to the radio. I have an old hang-gliding radio and I just tested the rubber duck antenna from that, and it also came in with a SWR of 20. I tried holding the connector in my hand (I understand handheld radios use the pilot as a groundplane) but it didn’t seem to make any difference.
SWR of 25-30 means something is certainly broken in that antenna.
It becomes a bit clearer if instead of SWR you think in terms of return loss (where high values are good – return loss means that for a given input, how much of it comes back. A perfect match (which never happens) would mean an infinite return loss (and a perfect open circuit or short circuit would give 0dB return loss).
An SWR of 1.5 means a return loss of 14dB. In other words, if your transmitter is outputting 1 watt, only ~40mW is being reflected back and not absorbed by the antenna.
An SWR of 30 means a return loss of only 0.5dB. If your transmitter is outputting 1 watt, 900mW is being reflected back (and only 100mW being absorbed by the antenna).
As you can see from this, an antenna with an SWR of 30, or return loss of 0.5dB is most definitely broken.
Hmm…
Bought myself a cheap SWR / power meter and built a ‘bazooka’ antenna that gives me an SWR of 1.5-2 across the band and a power reading of about 1.5 watts.
The SWR reading on the rubber duck antenna that came with the radio is about 25-30. I wonder whether that’s how it normally is, or whether there is something wrong with it e.g. a wire broken inside.
I don’t think I can fit the bazooka antenna in the aircraft, but next time I’m at the airfield I’ll walk to the far end of the runway and see whether it works better than the inbuilt one. It will tell me whether I’m on the right track, at least, and might save me from needing to buy a new radio.
I have been wrestling with 4NEC2 to design something that will fit in my aircraft and have the bandwidth required for airband radio. All I have managed so far is to give myself a headache.
kwlf wrote:
I have done a fair amount of work trying to make an external antenna in an attempt to gain a longer range. At some points and some frequencies, it wasn’t very well matched to the transmitter. I might even have pressed ‘transmit’ once or twice with it disconnected. Still not ready to install. I suppose it’s possible that I’ve broken the radio whilst playing.
Some of the Yaesu amateur band radios are notorious for frying their transmitter finals if a badly matched antenna or worse, no antenna at all when the transmitter is keyed up.
However, if you know any radio hams, they’ll usually have a power meter which can be used to make sure the transmitter is indeed transmitting at rated power.
Larger installed antenna connected via coax and BNC connector
A 1.5 Watt radio with a rubber duck is not likely to acheive any more than you are getting. Connect it to a proper quarter wave antenna with a ground plane and you might get somewhere.
Yes you can charge it. Needs something funny like 10.7v which I guess is easy enough but involves ordering connectors. For the cost of my time I figured it would be easier to order a new charger but got sent the base station instead!
Do you mean that you replace the short stub antennae with a longer directly attached antenna, or a larger installed antenna? Is there any in particular that you would recommend? Could be useful with a new radio even if it didn’t work out in the short term.
kwlf wrote:
The charger has gone AWOL so I have been using the AA battery pack rather than the Lithium pack that came with it.
I believe the Yaesu will charge the lithium battery pack via the “ext DC” port on the side of the radio. Slower than the base, but still.
All handhelds used on our club field seem to have aftermarket antennas installed (instructor watching student solo, parachute control person), or are hooked up to a fixed base antenna (eg. glider control trailer).
