How to best choke a receiver feedline

This is no antenna, it is a joke, a bad joke.

w.

It is a perfectly acceptable active antenna, and works as well as any other short active antenna.

The comments about choking the feed-line are quite reasonable, it you have an antenna high up in the clear you don't want signals, particularly local noise, picked up on the feeder being fed to the receiver.

Jeff

An acceptable choke can be a coil made of the feedline coax, correct? My understanding is you have to match any magnetic material to the frequency in use while an air core doesn't have that complication.

Depends on the frequency in question.

True, but at lower frequencies it is not possible to get enough inductance without a magnetic core of some sore in a reasonable size.

Jef

Hmm, everyone has an opinion, is yours based on testing one?

Anyway, I found my problem was not the feedline. I started turning off breakers and one of them shut down the buzz. Two sources of buzz were on that breaker and outdoor light with IR sensor and my garage door opener. I had a very minor buzz left, audible but didn't show up on the S meter. That was cleared with an isolation transformer and lifting the ground wire. Now I can receive 200kHz beacons, AMBCB, 80 meters, 40 meters 10 meters and 28 MHz CBer's. So it works, do I have anything to compare it to, not yet, but I'll be putting up a long wire soon.

Mikek

Btw, the antenna is quiet, without any chokes. I don't know if running the coax inside the metal mast helped, the mostly underground feed line probably did. Oh, I just realized I do have a choke at the bottom of the mast, just before the feed line goes into the ground. I'll remove that tomorrow and see if it's needed.

Helmut, I got my long wire up. 16ft high sloping up to 50ft high. It's 132 ft long plus another 16ft down and 4 more ft into the house. I tested from 211kHz to 1600kHz because that's what the antenna switch on my the radio allows.* My active antenna is better at 211kHz and much less noisy, at 325KkHz the signal strength is about equal, but still the active antenna has less noise. In the lower half of the AM band the long wire is equal or 1 S unit higher in signal strength. In the upper half of the AM band it is about 2 S units higher signal strength. The long wire is always noisier. The Active antenna is preferable. In fact the active antenna has less noise on every band where I tested,

5MHz, 10MHz and 15MHz. I still want to hook up an external antenna switch and test it at night,

but right now, the active antenna is clearly the winner.

I'm not in a particularly noisy area. In the middle of the AM band,

1025kHz (mid afternoon), I have 1 S unit on the active antenna and 3.5 S units on the Long wire.

• I have an Icom R71a, the radio has two antenna inputs, a UHF connector input and a long wire input. The antenna input is manually switchable up to 1600kHz and then radio takes over and only the UHF antenna connector is used. Hmm, for some reason my unit switches at 1598Khz.

Mikek

I wonder what exactly you are doing. Where is the active antenna placed? I would put it outside, a few meters away from the house in a free space and use shielded cable for connections.

Your long wire antenna is end fed, that means, it is unsymmetric, if I understand you correctly. And the wire goes unshielded into your house. This is the second worst scenario one could imagine, the worst being no antenna at all. End fed antennas should have a 1:9 balun at the end and connected via coax.

There is always room for improvement, the best of all antennas does not exist :-)

OE8UWW

I put the active antenna about 30ft from the house, up 24ft. The coax is buried in PVC from the antenna base to the house. The last 4ft at the top of the metal mast is pvc pipe, and the coax runs inside the steel mast.

That's a good point, although, my radio is made to accept a long wire antenna. I do think the change is worth doing, that will allow me to use a coax switch to make it easier to compare antennas on all bands. Rather than just AM, that the antenna switch on the radio allows. I did some night time testing last night and found the long wire has directional characteristics that help eliminate co-channel interference. The active, being omni picks up stations from all directions, making it less desirable at night when the atmosphere allows more signals to arrive.

After I get the 1:9 balun put up, I have an antenna phasing unit that I'll be able to experiment with and help eliminate co-channel interference.

Nope that's right. At one time I had a rotatable Flag with a variable termination, that was quiet and directional even on the AM band. Mikek

I'll need to put a little more thought into the 1:9 balun issue. One reason I wanted a long wire is so I could experiment with Crystal Radio. I'll need to figure out a way to switch from high impedance to low impedance balun fed. Mikek