LF: RE: Re: running a quick test beacon on 472.9. G7NKS. testing my revised Hafler PA set up.

[James Cowburn <jim.cowburn@outlook.com>]

Hi Alan

 

Thanks for the very useful insights here.  I agree that is almost certainly locally generated hash.  When I’m back from my imminent 4 week work trip, I’ll start the “hunt”

 

with best regards

 

 

Jim

 

Dr. Jim Cowburn G7NKS     IO92ub

 

Biggleswade  UK

 

Details on QRZ.com

 

From: owner-rsgb_lf_group@blacksheep.org [mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of Alan Melia
Sent: 10 June 2018 22:18
To: rsgb_lf_group@blacksheep.org
Subject: LF: Re: running a quick test beacon on 472.9. G7NKS. testing my revised Hafler PA set up.

 

Jim sadly the answer is not really a ''low noise antenna''  (try a dummy load if you are determined :-)) )

 

I am afrain the first thing to do is find the source of the noise and try to kill it.  The first thing to do is check your own premises by sitch the supply master switch off. Listen on battery powered rig and note the reduction. At the levels you are quoting I am sure some of this is self generated. I got my mean noise levells downto a couple of microvolts from a 10m vertical alongside the house with 130m of top-load.

 

A waterfall plot is quite useful for diagnosing possible sources.

 

Do this before you expend any time money and effort on something that may work well for someone else. (NB mini-whips were developed for a specific appartment problem where ferro-concrete was the build material......they dont necessarily work with our brick walls.)

 

A loop can be very useful for DFing the sources, but did not work for reception for Roelof.

 

I started quieting my station around the late 1990s. Ok it has got worse in some areas but better in others. Small SMPSUs often operate way higher than 136kHz now, but many previously quiet ''white goods'' was SMPoer controllers for efficiency eg fridges and freezers, not to mention the IoT. Many SMPSUs create more RFI when ''off' that when powering something. By ''off'' I mean in standby......TVs can be bad for this

 

I moonlight on the RSGB EMC committee so have some experience and useful contacts.

 

Best Wishes

Alan

G3NYK

 

 

----- Original Message -----

From: James Cowburn

To: rsgb_lf_group@blacksheep.org

Sent: Saturday, June 09, 2018 5:46 PM

Subject: LF: running a quick test beacon on 472.9. G7NKS. testing my revised Hafler PA set up. Can see it on B'ham grabber. thanx fer any other reports

 

Hi All

 

running a quick test beacon on 472.9.   G7NKS.  testing my revised Hafler PA set up.  Can see it on B'ham grabber.  thanx fer any other reports.  Message repeats every 5 mins @ 5wpm. 

 

Will leave it running for couple of hours or so

 

approx 0.5W erp from a 10m vertical with 3 x 30m top wires (running NW away from vertical )

 

ELAD FDM duo  0dBM output into cheap EBAY 1w broadband amp into Hafler 9505 as per W1TAG designs etc.

 

Will give WSPR a run later but having the devils own job with getting WSJT-X to be stable, keep getting the “hamlib dll “ error after a couple of cycles.  Very frustrating .

 

Also getting the ELAD to talk to HRDv5 and DM780 was a nightmare, but eventually solved with virtual audio cables etc but certainly not intuitive or easy.

 

Strangely, the Hafler P4000 puts out a bit more power as “stock” than the 9505 so am thinking about removing the feedback cap as discussed in the various W1TAG pages but can’t seem to work out how to open the case of the 9505!

 

Jay/John – any tips?  Is it the allen bolts?

 

Next thing is to lower S7-S8 noise on separate Rx antenna.  Have tried using Tx antenna which is 15m away from house but top wires go over house and so are prob picking up noise.  Current separate Rx antenna 10m vertical and 3 x 30m top wires also pass over house.

 

Any suggestions as to a good low noise Rx antenna most welcome.  I’ve tried a miniwhip but even when remote mounted on wooden pole with earthed braid at house entry it is still s8 noise.  G3XIZ suggests a loop, he’s probably right, but any other “quick and dirty “ ideas appreciated

 

The ELAD via the 0dBm is excellent as an exciter and will generate RF down to 5khz, so after some judicious coil winding, I’ll be trying LF again and then the heady lows of VLF.  My best previous Dx on 8.9khz being 500m!  (thats metres not km!)

 

I may try Roger’s G3XBM earth loop set up, but last time it didn’t work well but as I’m out “in the boonies” ~I don’t think I have much in the way of “buried Utilities assistance”

 

Cheers for any reports

 

Mal (KEV) you must be able to hear me with your monster set up in Scarbs!!

 

 

 

with best regards

 

 

Jim

 

Dr. Jim Cowburn G7NKS     IO92ub

 

Biggleswade  UK

 

Details on QRZ.com