Date   

Re: VLF/LF/HF Active Vertical Antenna...5 kHz to 30 MHz Discontinued!

Robert, VA3ROM
 

Thanks, Chris, that's great to hear!

It's the only antenna that I can put up for spotting MF and LF WSPR beacons feeding my KiwiSDR receiver (setup for 8 receiver channels) plus the 2nd antenna port feeds my VLF SID receiver (19-27 kHz). The only issue I had with the older 100 ma consumption unit was the green LED burned out for some reason. I may open it up this summer and replace both red and green LEDs with resistorized versions. They are way to bright for my eyes and I suspect that something cause a power surge because LEDs usually don't "burn" out unless something went awry. Otherwise, it's working fine for the past two winters that have been extremely wicked even for this Canuck!
73


Re: Loop Antenna + on 40m

Jon Hall
 

thanks for the comments Chris.
Good point about the efhw [yes 40m] that had'nt crossed my mind.
Its no real deal-breaker, I can just swop over as required.

Overall very impressed with the CCW Loop+ , a great companion for the sdrplay..
ATB, Jon


Re: Loop V L.O.G.

Simon
 

Ok

In that case, if possible can you compare WINS on 1010 between the 2 later tonight? ( wins near enough always there, atleast the carrier is always there.) listen on 1010 usb..
Nw facing..

Interested to see results.
Simon..


Re: Loop V L.O.G.

Oyster Town (G0IFS)
 

N.W ---S.E  and i can go 90 degrees from that next.


Re: Loop V L.O.G.

Simon
 

Hi

What direction is the card loop facing?

Simon


Loop V L.O.G.

Oyster Town (G0IFS)
 

The initial results of a comparison between a 2 metre sides cardioid loop (660 ohm resistor in top leg) and loop on ground with 6 metre sides both fed with CCW Beverage amplifier are a
slight improvement in signal to noise with the cardioid loop. Listening mostly on 160 metres. The loop of course is fixed in one direction so will be interesting to fix loop to a different fence panel! 


Re: Loop Antenna + on 40m

Chris Moulding
 

Hi Jon,

It could be several things that affect the performance of your loop.

The first thing I would do would be to look at the background noise level and compare it with say 80m and 30m. 80m should be the highest figure, 40m next and 30m the lowest.

It that test checks as expected then maybe it's the time of day that you listen to 40m . I've always thought of the 40m band as being like Dr Jekylll and Mr Hyde! It can vary between a local NVIS band in daytime if the sunspots are high enough to an all out DX band at night If the daytime sunspot figure is not high enough then there is usually very little activity in daylight.

Another possibility is that it's being affected by your EFHW. I would hazard a guess that it's resonant on 40m. If so it's possible that it's blocking some RF on 40m from reaching your loop.

This can also work the other way. I once tested a version of a MiniWhip antenna which gave outstanding results on 40m. It was only later that I realised it was 2m from the end of a 40m dipole and it was capacitively coupled to the end of the dipole.

The immediate surroundings of an antenna can have some strange effects on it.

Regards,

Chris


Loop Antenna + on 40m

Jon Hall
 

looking for advice / suggestions ...
I have the CCW loop antenna + with DC power unit. That is connected to sdrplay box.
I monitor from 160m - 2m and am well pleased with the results across this range.

I also have a efhw going down the garden.
Yes the wire is slightly better, but the loop works very well.
BUT [there's always a but]
On 40m the loop seems very deaf [all others bands are good]
The actual loop is the same length as the wire supplied, but I use a 1" stainlees steel strap.
Any ideas why only on 40m that I receive very little.

Regards, Jon.


Re: At what frequency(ish) does a small receiving loop lose directivity?

Chris Moulding
 

Looking at your example of a 1.2m loop it will have a full wave resonance like a quad loop at 79.6 MHz.

On that frequency the maximum gain will be broadside to the loop..

At low frequencies where the loop is a small fraction of a wavelength the sharp nulls are broadside to the loop.

You will probably see the loop lose it's directivity as it changes from one mode of operation to the other around 25 - 30 MHz..

Regards,

Chris


At what frequency(ish) does a small receiving loop lose directivity?

Kev Haworth
 

LAA+ now running a 1.2m loop from 10mm refrigeration pipe.

One big difference is that I'm having to reduce the RF Gain on SDRUno far more than with the Kunifer pipe, which I presume means the Refrigeration pipe is driving the amp with more gusto..

What sort of frequency does a loop with this configuration stop exhibiting directivity?

ODX since implementing this recent change are NDB in Croatia, 360Khz ish, 15m sw several YB (Indonesia) stations and plenty of west coast stations on 17m.


Re: Low Band Receiving aerials.

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


Re: Low Band Receiving aerials.

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







Re: Low Band Receiving aerials.

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


Re: Low Band Receiving aerials.

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.


Re: Low Band Receiving aerials.

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


Re: Low Band Receiving aerials.

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!


Re: Low Band Receiving aerials.

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


Re: Email problems?

Simon
 

No ..i cant see it ( he he.)

Simon


Re: Email problems?

scanmil
 

Thank you, I've been trying to get hold of Chris since January 4th via email but no replies, decided I would try on here but no reply either, thought something must of been wrong on my end and I was the only one able to see it.

Cheers,
Adam.


On 15/02/20
21 11:00 pm, leslie norton wrote:
Yes they can be seen by everyone on the mailing list

On 15 Feb 2021, at 11:57, scanmil via groups.io <scanmil@...> wrote:

Would someone be kind enough to confirm if my messages to the group can actually be seen by others, besides myself??

Cheers,
Adam.



Re: Email problems?

Craig
 

I see it

On 2/15/2021 5:57 AM, scanmil via groups.io wrote:

Would someone be kind enough to confirm if my messages to the group can actually be seen by others, besides myself??

Cheers,
Adam.

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