Adding an External Antenna to an Ultralight.


John H. Bryant <bjohnorcas@...>
 

I've now "successfully" added an external antenna port to the SRF-39FP, my DT-200VX and my E100. In each case, the units seem to work marvelously well with the external antenna, but each also seems to have picked up a bit of some sort of distortion when the receiver is used without the external antenna plugged in.... The audio seems muddy/dirty and I'm not certain that the sensitivity matches stock, either...... yet everything is better than good with the external antenna hooked up.

My goal was a means of attaching an external antenna that would:

1. Give me full effect of whatever external antenna was attached
2. Suppress or bypass all of the RF crud that is normally flying around in the shack when I DX... computers, TVs, digital read-outs, etc.
3. Let the radio operate normally when an external antenna was not in use
4. Either did not modify the radio at all or was easily reversible

If I had to give up one of those goals, it would be #3.... I don't mind having these radios as specialist DX machines, but I'd rather not. The new distortion seems worst on the E100, though at least a bit of weirdness is apparent in all three models.

As I thought about this, it also occurred to me that I'd not adequately tested the Gil Stacy approach of using a coupling coil on a tuned ferrite boosted bar (see his article at dxer.ca.) I've got a 12" x .75" version of the Booster Bar and I think that I'll put together a small one like Gil's and attach pick-up coils and BNC connectors on both. That would then give me five different things to test.

I think that I'll delay my testing until I get out to the NW where I can test their performance in a strong RF environment (my house near Vancouver, BC) and at Grayland. So, the "Rest of the Story" will be done sometime in early June. In the mean time, I'd love to hear from anyone else who has tackled this problem.

John B.
Stillwater, Oklahoma, USA
Rcvrs: WiNRADiO 313e, Eton e1, NRD-535(kiwa-mods)
Antennas: 700' NE/SW mini-Bev, Wellbrook Phased Array (pre-production version)