I've had an interesting, puzzling, problem for the last few days. I recently swapped vehicles, removed the VHF/UHF and HF radios from the truck, almost got stuff re-installed in the new car. Same radios, same antennas, the routing of cables is a bit different (antenna and power), but basically the same old set up just in a new location.
Had to use a mag-mount antenna for the VHF/UHF radio till I could get an adapter to convert from NMO to '239' type mount. Just happened to have one so not biggy, right? Also had to 'adapt' a rubber-duck antenna from a scanner for use on an APRS transmitter, did, and it worked. The only big problem was finding the @#$ 3/4" hole saw for the NMO mounts! I know I took it out of the old truck when cleaning all the stuff out of it at the car dealers, just didn't know where it ended up here at home. (Saved it from getting 'lost' by putting it in a special place, you know?)
Found the hole saw! Drilled a hole, ran the cable for the APRS thingy, worked just dandy! Almost. Kept getting interference in the 2 meter radio every time the APRS thingy sent a burst. What's with that? Never did that before. So, did the 5 gallon bucket of ferrite cores trick with the power lines and feed lines. Still had the interference. Okay, so did the choke thingy with the power lines. Had an old ferrite pair of 'rings' from an old power supply. Removed 2 or 3 yards of wire from it, rewound it using two conductor cable, put it in the power line. No help. Aw man! What's with this? It worked good in the truck, won't in the new car.
[Was using a 1/4 wave antenna on the APRS, and a Comet dual bander on the VHF/UHF radio, only difference was used a 5/8 wave on the APRS before. A @#$ 1/4 wave antenna just can't be the problem, could it? Checked both antennas with an antenna analyzer, neither was 'perfect', but certainly good enough. So, more ferrite torroids. Probably around 10 pounds altogether, car is starting to lean to one side.
The adapter for the NMO/239 thing came in! Did more antenna changing than you'd ever believe, both radio and APRS. Same @#$ thing happening. The only remaining difference was the mag-mount. So, drilled the second hole. Mounted the radio's antenna. Bite my bippy! Problem solved! Who'da thunk it?
It isn't the 'typical' type mag-mount either, it really is a good one, and strong. It's worked just dandy in other applications, but not on 2 meters. Odd.
So why didn't I drill the holes to start with, especially since I don't like mag-mounts in general? A 'form fitted' headliner, and 'curtain' air bags over the doors. Air bags scare me, I definitely do not want to trigger them! And there's a 'ledge' that you have to get around along the sides of the car's roof where they are mounted. Had to work my 'nerve' up to do that. Oh, and it's such fun! Ever had to use two 'snakes' to fish a cable from one place to another? Or remove two over head dome lights just to find the @#$ cable? Those lights get hot enough to melt steel, I swear, and I've got the burns to prove it!
Damn! Glad that's over. But what about the screwdriver antenna and HF? Uh, forget it. There's just no way I can think of to mount that monster. And remote head or not, I can't find anyplace to mount the radio. Ain't that the pits?
If all this was so much trouble, why did I swap vehicles? First, the new one is red! I love red! I got a red flash light, a red fan on the desk, a red cell phone. (Wear red thongs, which is really none of your business, but the 'blue-hairs' love that.) Not to mention that the truck got about 11 mpg and the new car get's about 28 mpg in town (and I do delivery stuff). If I keep working for the next 20 years or so, it'll pay for it's self, right? Besides, it's red... :wub:
- 'Doc
The moral to the story is that those analyzer numbers don't always tell the whole story, and in certain applications a mag-mounted antenna is going to cause problems no matter how 'well' it seems to work.
Had to use a mag-mount antenna for the VHF/UHF radio till I could get an adapter to convert from NMO to '239' type mount. Just happened to have one so not biggy, right? Also had to 'adapt' a rubber-duck antenna from a scanner for use on an APRS transmitter, did, and it worked. The only big problem was finding the @#$ 3/4" hole saw for the NMO mounts! I know I took it out of the old truck when cleaning all the stuff out of it at the car dealers, just didn't know where it ended up here at home. (Saved it from getting 'lost' by putting it in a special place, you know?)
Found the hole saw! Drilled a hole, ran the cable for the APRS thingy, worked just dandy! Almost. Kept getting interference in the 2 meter radio every time the APRS thingy sent a burst. What's with that? Never did that before. So, did the 5 gallon bucket of ferrite cores trick with the power lines and feed lines. Still had the interference. Okay, so did the choke thingy with the power lines. Had an old ferrite pair of 'rings' from an old power supply. Removed 2 or 3 yards of wire from it, rewound it using two conductor cable, put it in the power line. No help. Aw man! What's with this? It worked good in the truck, won't in the new car.
[Was using a 1/4 wave antenna on the APRS, and a Comet dual bander on the VHF/UHF radio, only difference was used a 5/8 wave on the APRS before. A @#$ 1/4 wave antenna just can't be the problem, could it? Checked both antennas with an antenna analyzer, neither was 'perfect', but certainly good enough. So, more ferrite torroids. Probably around 10 pounds altogether, car is starting to lean to one side.
The adapter for the NMO/239 thing came in! Did more antenna changing than you'd ever believe, both radio and APRS. Same @#$ thing happening. The only remaining difference was the mag-mount. So, drilled the second hole. Mounted the radio's antenna. Bite my bippy! Problem solved! Who'da thunk it?
It isn't the 'typical' type mag-mount either, it really is a good one, and strong. It's worked just dandy in other applications, but not on 2 meters. Odd.
So why didn't I drill the holes to start with, especially since I don't like mag-mounts in general? A 'form fitted' headliner, and 'curtain' air bags over the doors. Air bags scare me, I definitely do not want to trigger them! And there's a 'ledge' that you have to get around along the sides of the car's roof where they are mounted. Had to work my 'nerve' up to do that. Oh, and it's such fun! Ever had to use two 'snakes' to fish a cable from one place to another? Or remove two over head dome lights just to find the @#$ cable? Those lights get hot enough to melt steel, I swear, and I've got the burns to prove it!
Damn! Glad that's over. But what about the screwdriver antenna and HF? Uh, forget it. There's just no way I can think of to mount that monster. And remote head or not, I can't find anyplace to mount the radio. Ain't that the pits?
If all this was so much trouble, why did I swap vehicles? First, the new one is red! I love red! I got a red flash light, a red fan on the desk, a red cell phone. (Wear red thongs, which is really none of your business, but the 'blue-hairs' love that.) Not to mention that the truck got about 11 mpg and the new car get's about 28 mpg in town (and I do delivery stuff). If I keep working for the next 20 years or so, it'll pay for it's self, right? Besides, it's red... :wub:
- 'Doc
The moral to the story is that those analyzer numbers don't always tell the whole story, and in certain applications a mag-mounted antenna is going to cause problems no matter how 'well' it seems to work.
