My SSTRAN with base-loaded antenna has been operating for about three months now. When I first set things up, I had a fairly strong signal out to 1 mile (in the vehicle). Lately, I have noticed that the signal is more noisy past 1/2 mile. Just now, I got on the roof and re-checked the tuning and ground connection. When originally installed, I was able to get a full 13VDC at the test points on the transmitter. Just now, I can only get 12VDC maximum. I tried re-tuning the antenna and the trimmer cap on the transmitter board, but can't do better. So, what the heck has happened?
I thought that maybe the hotter weather was a factor, but Phil at SSTRAN has indicated in the past that with the temperature range of the components used, this shouldn't be an issue. The copper radiator of the antenna has weathered after three months, but would surface oxidation cause a significant change in the resonance of the antenna? And if so, wouldn't I have been able to compensate by re-tuning the length of the radiator? The only thing I did not change was the tap on the loading coil. I'd have to drag a soldering iron onto the roof for that.
Any suggestions?
My thought would be that while the components are stable within the temp range, the amount of moisture in the soil may be less than it was due to the season. That would reduce ground conductivity, and as such reduce the efficiency of your system, which I *think* might be able to account for the symptoms you describe.
Daniel
That may be a possibility. My ground is rather indirectly connected to earth. I am grounding to a cold water pipe that feeds the evaporative cooler on the roof. It is the nearest thing to a ground and only requires a short wire from the transmitter.
I would clean all the conections, your ground, coil to antenna and also you antenna its self. I had the same problem about 4 months ago so I re did all my conections and that fixed the problem.
Brian
www.freewebs.com/underdogradio
Mojoe,
When I used the plumbing as a ground for my ham station there was random scratching interference which correlated with the a/c running or someone walking on the floor above. It turned out to be that a water pipe was touching a heating duct. I "redressed" the pipe and all was well. I have since redone this with a separate ground wire to the electrical stake.
This is just a thought for your situation in that maybe something has changed in the plumbing. I would follow Brian's suggestion first but thought I would offer this longshot idea.
Neil
Do you have any trees near your set up? Leaves/trees will react with your xmtr. Sounds like the trees got their leaves and thats eatin' up your signal..
~Don
Rattan gets the prize. It rained last night and today, I noticed my range is better. It's not quite as good as it originally was, but it is noticeably better. I guess I'd better practice my rain dance 🙂
All of the comments here are very good and possible.
Just keep in mind that the Part 15 antenna design has an extremely narrow bandwidth at resonance and the antenna will go off resonance easily due to temperature changes that increase or decrease the coil's distributed capacitance.
A tuner at the coil tap point is the best idea for making touch ups. However it takes not only allot of coil but capacitance for a mediumwave tuner.
Dan
Correcto Mondo, Dan..
Those operating with a Rangemaster can expect to concentrate on ground conductivity.
Everyone has contributed important and technically sound points here! That's refreshing. It’s great to see real contributions. The reality of living with FCC rules limiting antenna length makes details so critically important.
One very important aspect of antenna and ground connections is the concept of a "gas tight" connection. Any clamp point needs to be tight enough to prevent any air or moisture infiltration that can cause corrosion of any sort. This concept has historically been proven with aluminum electrical wire. It's OK to use aluminum wire only if it is clamped properly to prevent corrosion of the aluminum wire at the junction.
Even though we don't use aluminum wires in our antenna installations, the same requirement is important because the antenna parameters are so critical. Any clamp point is suspect and needs to be done carefully.
Clamp points can exist in the ground system, depending on how it is implemented. One obvious point is the ground rod. A clamp on the rod should be done carefully. Make sure the clamp and rod are clean and bright, and then tighten the clamp enough to guarantee that no air or moisture can penetrate. Good, bright, well-flowed solder connections are best, but can't always be done.
Another point of concern is any clamp point on the antenna, such as the length adjustment clamp, should get careful attention. Be sure to clean the copper thoroughly. Sandpaper or steel wool should be used to brighten the copper thoroughly before clamping. Also, be sure to tighten the clamp as tight as possible to prevent air/moisture infiltration.
Ground moisture variations affecting the ground system can be alleviated by using more and longer ground radials. A single ground rod will be very sensitive to ground moisture variations. On the other hand, a radial wire system provides a ground reference that is less sensitive to ground moisture.
All ideas are welcome for improving antenna performance stability. Bring on the ideas!
Phil B