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Re: LF: From M0DSZ by M0DSZ Loc IO82LS 0.136 MHz (2200m), OPERA, -36d

To: [email protected]
Subject: Re: LF: From M0DSZ by M0DSZ Loc IO82LS 0.136 MHz (2200m), OPERA, -36dB
From: LineOne <[email protected]>
Date: Fri, 29 Jul 2016 15:10:25 +0100
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Home-constructed, originally mixing 2 Philips crystals (fine for QRSS) but now with an alternative plug-in digital oscillator. 3 modulation setups are available, straight (keyed for QRS or Opera), phase modulation (for various psk) and quadrature modulation (using I & Q from a PC, good for WSPR). It delivers over 1W into 75 ohms and is all made on Veroboard.

Audio-type amplifiers form the PAs and, by adding a large electrolytic in the output, I can use them at VLF. One runs to 136kHz and the other can do 477kHz but gets somewhat hot. Experiments with switching FETs have only resulted in quantities of cooked devices.

Power supplies are all linear as I've always had trouble keeping the switching noise out of anything, hence the expense.

73 from Hugh

On 28/07/2016 18:22, Graham wrote:
Hi Hugh
 
What  instrumentation are you  using ?  dummy load  to  match the  amp and rf voltmeter could be a  starting point , I don't think any of my  bridges , work at 136 ,  apart from the  Rf probe + attenuators ,  477 , the  hf swr  meter and bird inserts [ with cal chart] work fine ..
 
No ferrites , I use  air-cored inductors and a  tapped  one   as  auto-transformer , things may get a  little  over size  at  136
 
Tx wise , PC with  sound card  as the  audio  source / decode  ,   the  exciter is  a  Racal  MA 1723 , will  run to  136 ,  fine on  477  , that  feeds , via a  stepped  10/1/0.1 dB attenuator to set the  drive ,  a  resistive splitter  and  two skanti  trp 8500 , 250 watt  out ssb linear  pa  modules  , which are combined , with a  [lucky-find]  5  port combiner , the  whole thing  is  wide  band, the  only  tuner is  the  ATU ,  variometer  for  477  and a  racal 1k  auto tuner  for  HF  , same  Ae , can use it on HF, but its a  bit  back to  basic's ,
 
I use the  audio  drive  on Opera , with the  change over  hard keyed  from the  com-port , the  racal set up is getting on in life , but  effective .. as long as it  passes self-test ...
 
Psu  is a  ebay special , some  sort of  phone  exchange , switchmode 50 volts , not sure on the  max amps ,  but the  plate  asks for a  35 amp 240v  supply , which by the  size of the copper  busbar out put terminals  , 150 A  is probably about right ,  but not  from  a 13 amp  plug !, the  other is a  old farnell  variable 20 amp ..
 
Q What exciter do  you  use  Hugh ?
 
73-Graham
G0NBD
 
 
 

 
From: LineOne
Sent: Thursday, July 28, 2016 11:52 AM
Subject: Re: LF: From M0DSZ by M0DSZ Loc IO82LS 0.136 MHz (2200m), OPERA, -36dB

Effectively linear amplifiers, class AB2, one 300W and one 500W dc input with very low output impedance. The antenna current difference is less than 5% so the expense of a new PSU, case and so on is so far wasted. Matching for the 500W is awkward as the transformer primary for the 500W may need the odd half-turn which is difficult with a toroid.
I can't send on Opera & WSPR consecutively without some delay to reset the COM1 port.

Anyway I'm happy to monitor both simultaneously by request or if there's anyone on. QRSS at the same time is not yet possible because I only have COM 1 available and Spectrum Lab doesn't like sharing. What's your setup?

Hugh, M0DSZ

On 27/07/2016 22:22, Graham wrote:
Just spotted you  on the  psk-map  Hugh
 
There's a  square  law  , to  the  current , doubling the  power , gives  a  fractional  increase .. but still  + 4 dB over the  decoder limit ,  ~  + 9 over the  dynamic detector
 
What are you running, what's  the  set  up ?
 
73-G,

From: LineOne
Sent: Tuesday, July 26, 2016 11:27 AM
Subject: Re: LF: From M0DSZ by M0DSZ Loc IO82LS 0.136 MHz (2200m), OPERA, -36dB

I'm pleased someone was monitoring, I suspect conditions were not too good. This is a new linear amplifier but, in spite of having more input power, doesn't produce much more antenna current.

Hugh, M0DSZ


On 25/07/2016 19:48, Graham wrote:
One ping this afternoon
 
Rx at Mon, 25 Jul 2016 16:17:22 GMT
From M0DSZ by PA7EY Loc JO22JJ
Frequency: 0.136 MHz (2200m), OPERA, -36dB
Distance: 530 km bearing 91°
Using: Opera v1.5.7/Rptr V1.6
Antenna: RX Op32
 
73,G



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