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| To: | <[email protected]> |
|---|---|
| Subject: | Re: LF: Re: Separate Receiving Antenna? |
| From: | "James Moritz" <[email protected]> |
| Date: | Sun, 16 Jan 2011 18:53:35 -0000 |
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| In-reply-to: | <[email protected]> |
| References: | <[email protected]><003301cbb568$1a159780$0401a8c0@xphd97xgq27nyf> <[email protected]> |
| Reply-to: | [email protected] |
| Sender: | [email protected] |
Dear Toni, LF Group, ...> It will be difficult to get a receiving antenna far away enough...>Unlike Mal, I have used seperate RX antennas for several years on 136k, due to local QRM picked up by the TX antenna. I am currently using both loops and a vertical for RX. The loops show no noticeable coupling to the TX antenna provided they are several metres from the downlead and loading coil. Actually they are directly underneath one end of the TX antenna wire at the moment. The vertical does have significant QRM induced by the main TX antenna, but this is greatly reduced by having a relay that disconnects the TX loading coil on receive, and de-resonates the TX antenna. The RX antennas are about 40m from the main noise sources, which seem to be the mains and telecom wiring in mine and neighbors houses. QRM is not eliminated by this seperation, but it is greatly reduced - enough to make operating possible, at least... I have used seperate TX and RX antennas at a number of QTHs now, because most locations seem to have noise problems for LF reception! I have usually found it possible to get good improvements in reception. The main thing is to find the best position for the RX antenna - moving it a few metres can make a big difference sometimes. Another useful measure is a 1:1 RF isolating transformer at the RX end of the feeder, to reduce "ground loop" effects. A 100m reel of RG58 coax has less than 1dB loss at 136k, so it is not too difficult to have the RX antenna quite a long way from the TX antenna. Cheers, Jim Moritz73 de M0BMU |
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