Low Band Receiving aerials.


Oyster Town (G0IFS)
 

Good morning,
Interesting topics on here. I am looking forward to better weather to proceed with the quest for improved signal to noise ratio particularly on Top Band.
I have tried most of the usual suspects, loops of all kinds, Log, bog, E field probes, passive and amplified using commercial and home brew construction. 
At the moment the best combination at this location is a mini whip phased against a well known commercial amplified steerable loop to cancel offending noises.
Next project 2 metre square amplified Cardioid loop, 1 metre circular Cardioid loop and another loop on ground as the last effort was not convincing.

Main HF transmitting aerials are doublet with 250ft top, open wire feeder to link coupled balanced matching units (one for each band), doublet 90 ft top and commercial trapped vertical.
None of them used for receive of course!


Simon
 

Hi

Don’t forget as the year progresses the ambient noise floor on 160 will be increasing..thus making it tricky to really test the lf antennas..

Keep us informed on how it goes please..

Mag loop Simon g0zen

Ps have tried running the doublet against a phaser


Oyster Town (G0IFS)
 

Hello Simon, 
If you were asking if i have phased against TX doublet-----yes but i prefer to keep TX feed separate from any phasing unit.
Receive aerials are routed via phasing unit to RX only input on transceiver. I can bypass phaser and select which receive aerial to route direct to RX input. 
I note subtractive or additive effects to noise or wanted signal when different TX aerial are selected or grounded.
Too close together of course!


Simon
 

Hi

Its very easy to protect the phaser/active antennas if using tx into phaser if thats the issue..??

The doublet should if you live in rf quiet area be quiet good rx on 160 assuming its high ish..oh to have a full size antenna!!!

I live in east London..tiny tiny yarden..so my 160m trx antenna is a big qro mag loop..i run that against a preamped crossed parallel loop ( with phaser.) aiming at the local noise ( smpsu 200m away)
Obviously its in the 100w out from rig not the big amp. It does work well..cqww 160 ssb soon..hopefully get more S America qso’s done..Chile and Argentina would be nice!! Hence the rush in getting the cardioid loop array working..Hearing anything here in London is a challenge in itself!

Right now ( see other post as will be updated hopefully tonight.) am qc’ing/ tweeking the null steerer for the broadside big cardioid loops.

Looks promising..can now null out the s9 smpsu that the cardioid loops we’re hearing ( due to no 90 degree nulls on them.)..still not sure on a few issues..but thats not for here yet..preamps and loops amp by the way are cat5 feed with nw/se switching..

If you have the space endfire cardioid loops? Maybe even 4..

Simon


Oyster Town (G0IFS)
 

I am fortunate to live half a mile from the sea shore so noise not too bad.
The early home brew phasers had relay by-pass for TX but i prefer not to have too many contacts and impedance discontinuities in line.
All the Rx aerials have relay dis-connect for dc and feeder during Tx------just in case.
I try and use QRP where possible.
Good luck on your experiments, keep posting.


Simon
 

Hi

Surely the early phasers with ptt disconnect and now the rx antennas with similar is the same? Still impedance issues .. which really dont matter anyway, as long as all wiring kept short..
After all, linear amps, rigs etc use relays in rx or tx line and relays dont have 50r impedance..

Note i may have misunderstood your post..

Moving near coast i hope in a couple of yrs..big garden!!!

Yes will be keeping updates going..

Simon


David Cutter
 

There are microwave-rated relays that do a good job of 50 ohms and not really expensive if you are in to VHF+ I don't think these things matter much at HF and MF for receiving. It's not about maximum power transfer theorem it's about signal to noise ratio.

More of an issue if you are a high speed break-in cw operator is relay timing. If it's an issue then a proper sequencer might be needed for use with linear power amplifiers, but some modern rigs have adjustable timing to wait for relay strings to close/open.

David G3UNA

On 15 February 2021 at 22:23 Simon <ohhellnotagain@gmail.com> wrote:


Hi

Surely the early phasers with ptt disconnect and now the rx antennas with similar is the same? Still impedance issues .. which really dont matter anyway, as long as all wiring kept short..
After all, linear amps, rigs etc use relays in rx or tx line and relays dont have 50r impedance..

Note i may have misunderstood your post..

Moving near coast i hope in a couple of yrs..big garden!!!

Yes will be keeping updates going..

Simon







Chris Moulding
 

A few years back I built a prototype SDR transceiver capable of full break-in CW keying.

I used it with the CW Skimmer program in the CQ WW CW QRP Assisted section to become 2nd in the UK. No one was more surprised than me!

For the antenna change over relay I used a small Omron surface mount relay that had a very fast switching time including contact bounce of 3 mS. In other equipment I've run them at 150 W on HfF with very good isolation and VSWR performance.

Here is a link to the RS Components listing for the relay: https://uk.rs-online.com/web/p/high-frequency-rf-relays/8074107/

Regards,

Chris