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
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,
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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