Date   

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.


Re: Email problems?

leslie norton
 

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?

scanmil
 

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

Cheers,
Adam.


Re: PSK63 HF APRS is Back !

Chris Moulding
 

Good to hear that FlDigi can be used as a KISS modem.

I was really disappointed when I had to remove APRS Messenger but I could find no way to run the Visual Basic 6 programming software on Windows 10 to fault find the problems running it on Windows 10.

One question about running FlDigi in KISS mode. One of the strengths of APRS is that there is error detection in the protocol used on VHF 1200 bd and HF 300 bd that rejects packets with errors.

In APRS Messenger I added a simple CRC check to prove that the received packet was the same as the transmitted one and used it to reject or not igate packets with errors. I added an option in the program so that it would display packets with errors on the display so that a human operator could read an make sense of packets some errors due to fading on HF.

I've been having a quick read of the AX25 KISS protocol and I can see that it can detect framing errors but nothing about errors in the text sent over the air.

Stephen, can you confirm from your testing that it's rejecting packets with errors in the transmitted text?

It's an important point because if it allows packets with errors through then it would allow garbage to go to the APRS-IS internet system with incorrect positions and at worst case incorrect callsigns.

Regards,

Chris


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!


Re: PSK63 HF APRS is Back !

Kenny Witt
 

Great!  Been working with com0com for years.  Lots of possibilities there

Kenny, KC4OJS 


On Feb 14, 2021, at 5:11 PM, WA8LMF via groups.io <wa8lmf@...> wrote:


On 2/14/2021 4:54 PM, WA8LMF via groups.io wrote:

Ever since APRS Messenger was discontinued, I have been lamenting the loss of a vastly superior (compared to 300 baud AX.25 packet) HF APRS transmission mode. 

I discovered that the FLdigi multi-mode sound card app can act as a KISS modem to external applications.   After a considerable amount of testing, tweaking and experimentation, I have got FLdigi to work with various APRS clients on PSK63, MFSK16, 8PSK-250 and other modes provided by FLdigi.


Forgot to also mention:

The gateway page to my various mapping APRS igates/webservers for the various bands and modes is:

   <http://WA8LMF.net/map>




Re: PSK63 HF APRS is Back !

WA8LMF
 

On 2/14/2021 4:54 PM, WA8LMF via groups.io wrote:

Ever since APRS Messenger was discontinued, I have been lamenting the loss of a vastly superior (compared to 300 baud AX.25 packet) HF APRS transmission mode. 

I discovered that the FLdigi multi-mode sound card app can act as a KISS modem to external applications.   After a considerable amount of testing, tweaking and experimentation, I have got FLdigi to work with various APRS clients on PSK63, MFSK16, 8PSK-250 and other modes provided by FLdigi.


Forgot to also mention:

The gateway page to my various mapping APRS igates/webservers for the various bands and modes is:

   <http://WA8LMF.net/map>




PSK63 HF APRS is Back !

WA8LMF
 

Ever since APRS Messenger was discontinued, I have been lamenting the loss of a vastly superior (compared to 300 baud AX.25 packet) HF APRS transmission mode. 

I discovered that the FLdigi multi-mode sound card app can act as a KISS modem to external applications.   After a considerable amount of testing, tweaking and experimentation, I have got FLdigi to work with various APRS clients on PSK63, MFSK16, 8PSK-250 and other modes provided by FLdigi.

1)   FLdigi provides a KISS output over TCP/IP -- not a virtual serial port. This means that either:  Your APRS client must support KISS-over-IP -- Or that you do an IP<-->serial conversion for older com-port-oriented APRS applications such as UIview.   


2)   The IP-to-serial conversion can be doe with the freeware utility "com0com" and it's companion application "com2TCP"



3)   I am now operating FLdigi-mode igates on 30 meters and 60 meters  24/7, from my QTH in East Lansing, Michigan (center, more-or-less of the lower peninsula of MI.  

On 30 meters, I an using the same channel center as the classic 300-baud AX.25 packet APRS.  On 30M, place the radio on 10.147.60 MHz USB, which will place FLdigi modes with 1700 Hz audio center tones exactly on 10.149.30 MHz RF -- i.e. midway between the 10.149.20 / 10.149.40 tones of AX.25 packet APRS.   

On 60 meters, I am using US 60M "channel 5" (carrier freq of 5.403.50 USB). 


4)   The setup on each band is a Yaesu FT-857 with a 500 Hz Collins CW filter.   This is just wide enough to pass the conventional 300 baud HF packet APRS, and also the narrower FLdigi modes such as PSK63, MFSK16, 8PSK-250, etc.  Don't try wide modes such as Olivia 1000 or MT63 -- they just won't fit through the 500 hz passband.


5)   Full details on setting various APRS clients to work with FLdigi (including the IP<-->serial bridge if needed) are here on my website:

    <http://WA8LMF.net/FLdigiAPRS>



Stephen H. Smith    wa8lmf (at) aol.com
Skype:        WA8LMF
EchoLink:  Node #  14400  [Think bottom of the 2-meter band]
Home Page:          http://wa8lmf.net

-- APRS over FLdigi Modes  --
   <http://wa8lmf.net//FLdigiAPRS/index.htm>

60-Meter APRS!   HF NVIS APRS Igate Now Operating
   <http://wa8lmf.ddns.net:14447/>

Flying Digipeater!
   <http://WA8LMF.net/FlyingDigi>

11 Copies of UIview in Action on One Computer!  
Live Off-The-Air APRS Activity Maps
   <http://wa8lmf.net/map>







Re: twin turn loop on LAA+ and experimenting weekend.

Simon
 

Hi

Not sure if we on same page here..

I thought u we’re talking about 252khz..
Using cardioid’s on there nw or se gives me rte ireland or algeria radio..( depends upon which way loops are switched.) but i now think you were talking degrees..opps.

Now on 590khz..usb..( so as to remove lsb .) se direction no vocm..nw s9 or so vocm no splatter..

Remember cardioid loop has much lower angle of radiation compared to standard loop but does not have the 90 degree deep null..but with 2 and a steerer that i hope will be available..watch this space..

Pic of steerer being made..not finished yet..Will not be so untidy!!



The idea of the null steerer ( Chris pointed me at this.) is to allow the general direction of the broadside cardioid loops to be facing nw or se ( as mine are,) but to allow the null to be steerable around the loops..
How much/ large / size degrees steerable is to be seen..but in theory it should be alot..one hopes to be able to steer the null to 90 degrees to direction of loop..
Not tried this before..so learning..only used null steerer/ phaser to cancel noise on antennas..
rather alot of effort in making this null steerer though..( hand making pcb’s etc.) so i do hope it works!!if it does not then no great lose as it will make a good noise canceller..

Testing as soon as the Po decide to deliver some well late relays!!

Simon


Re: twin turn loop on LAA+ and experimenting weekend.

Kev Haworth
 

Simon.
If i 'Beam' directly to 252 , it is massive, 30 db over easily on the s meter. go 90 degrees against it and the cardioid drops it to s9,

I'm seeing lots of 'sproggies' spururious  on the cardioid though. back to a 'standard' loop i think..

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