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To : PSK31@WW.SYD.NSW.AUS.OC
De: Psk31 Digest <owner-psk31@aintel.bi.ehu.es>
Para: <psk31-digest@aintel.bi.ehu.es>
Asunto: Psk31 Digest V1 #202
Fecha: jueves 14 de octubre de 1999 4:33
Psk31 Digest Thursday, October 14 1999 Volume 01 : Number 202
In this issue:
RE: [psk31] QRP
[psk31] Lowfer/Medfer PSK31
[psk31] Fw: [dsp] DSP-10 2 meter transceiver September/October QST
See the end of the digest for information about psk31-digest
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Date: Wed, 13 Oct 1999 12:11:40 -0400
From: Charles Greene <cgreene@loa.com>
Subject: RE: [psk31] QRP
At 04:12 PM 10/13/99 +0200, Jan Olof Bergstén wrote:
>Hi Charles
>
>If your meter is redaing average (as most old meters do) you SHOULD have
>100% at tune and 50% at idle, otherwise you are overdriving.
>
>On my IC-756 I had 100% both in Tune and Idle, Peter PLX checked my signals
>on the air and they was ok, so he figured out that my Wattmeter in the
>IC-756 read PEP. I then connected my old Heatkit Wattmeter and on that it
>was 100 and 50%.
>
>As I understand of what you have written you have idle at 80% with 100 Watts
>and idle at abt 93% at 15 watts ?
>
>Best 73
>Jan, SM7ETW
Thank you for the information, Jan. I guess that, like yours, my
meter is not reading average power correctly. It sould read 2:1
tune to idle, but it isn't. I assure you, I am not overdriving. With
this setup, I typically get reports of IMD of -35 DB and comments
that the signal is very clean.
>> -----Original Message-----
>> From: Charles Greene [SMTP:cgreene@loa.com]
>> Sent: den 12 oktober 1999 14:32
>> To: Dan W. Dooley; PSK Mailing List
>> Subject: Re: [psk31] QRP
>>
>> At 07:49 PM 10/11/99 -0500, Dan W. Dooley wrote:
>> >I like this idea.
>> >
>> >Is idle power where we should measure our power output? How does that
>> >differ from power output in the "Tune" mode -clicking on the Tune button?
>>
>> Hi Dan,
>>
>> Idle power is 50% of PEP. On my rig, when I set up Tune to 100 watts,
>> Idle reads 80 watts or if I set tune at 15 watts which is a little more
>> accruate, Idle is 14 watts, so I'm sure that Tune and Idle are not the
>> same.
>> My power meter will not read correct PEP on SSB and Idle, as it is an
>> analog meter and it is not fast enough to follow the peaks in SSB.
>> I believe it is reading average power. I'll set up my scope and get a
>> good
>> reading and then let you know.
>>
>> >
>> >When I do that, my power output reads two watts. When I play the
>> keyboard
>> >of course the needle fluctuates rapidly between perhaps 1.5 to close to 2
>> >watts. When it goes into idle, it reads 1 watt.
>> >
>> >Set thus, I worked a PU2 this weekend. I calculated 5094 miles. So, do
>> I
>> >use the one watt idle or two watt key down power claims?
>> >
>> >Wow, if one watt's the reading then I got a whopping 5094 miles per watt!
>> >
>> >On the other hand, maybe the guy was kidding me and he's down the street
>> >from me rather than in Sao Paulo <grin>
>> >
>> >Dan WB5TKA
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Date: Wed, 13 Oct 1999 09:20:46 +0000
From: Peter Martinez <Peter.Martinez@btinternet.com>
Subject: [psk31] Lowfer/Medfer PSK31
From Peter Martinez G3PLX
Congratulations to Clint KA7OEI on the hardware implementations of
PSK31 for low-frequency work. Personally I think the hardware
implementations of PSK31 have been rather neglected. Perhaps this is
a side-effect of the software version being cost-free! Some
interesting applications of PSK31 have probably not yet seen the
light of day as a result. Clint's work is valuable in this respect.
Here's a few of my own ideas for exploring the PSK31 scene with
hardware for VLF and other areas:-
1. Transmitting "squarewave" PSK31, although it would be considered
very antisocial on HF radio, is a valid way of doing it when we are
not concerned with adjacent-channel QRM. I am thinking of underground
induction field communication at VLF, and other non-radio
applications where we are fighting the noise level and not the QRM. A
Class C power amplifier, designed more like a switchmode PSU than a
transmitter, fed with PSK31 generated with an XOR gate, will be ideal
for this task. Be careful that if this kind of transmitter is
connected to a very high Q VLF antenna, there can be disastrous
effects when the transmitter reverses phase and the high level of
stored energy in the antenna circuit is dumped back into the
transmitter! Check the reverse ENERGY capability of the transmitter
rather than the reverse POWER rating. This probably doesn't apply to
USA lowfer activity, but could apply to the European 136kHz
allocation where you might have a 1 kW transmitter to radiate the
permitted 1 watt e.r.p.
2. Note that if the transmitter is hard-limited in this way, the
receive filter in the current software PSK31 receive-side is not
quite optimum, since this is matched to the cosine envelope of the
software PSK31 transmit-side. Slightly better results (by which I
mean performance in Gaussian noise and not adjacent-channel
rejection) can be achieved with a filter matched to the square-wave
transmit envelope. The classic "Integrate and dump" filter (or the
equivalent using analogue delay lines) is right for this task, and is
quite easy to build in hardware. More good reasons to experiment with
simple hardware PSK31 receivers.
3. On HF the PSK31 receive signal is demodulated incoherently, by
comparing the phase of one symbol with the previous one. The
transmission is encoded differentially to match this, but we can gain
an extra 3dB of weak-signal performance if the path is stable enough
to let us demodulate coherently. We don't even need to reconfigure
the transmission coding to do this, since we can get the same answer
as differential incoherent demodulation by using coherent
demodulation followed by differential decoding. VLF applications,
whether radio or induction-field, are certainly stable enough. The
only penalty will be that it will take a little longer to lock in at
the start of a transmission, but we could easily switch between
incoherent and coherent if that's a problem. This is another area for
exploration with simple hardware demodulators.
4. Although QPSK is noticably better that BPSK on HF where there is
QSB and burst noise, when the limiting factor is Gaussian noise, BPSK
is better. This could mean that simple BPSK may be the best choice
for some non-HF applications of PSK31. The Lowfer/Medfer area might
suffer from atmospheric static which could mean QPSK had the
advantage there, but for underground reception of VLF, or laser
working, or perhaps even underwater acoustics, hard-limited BPSK
transmit and coherent integrate-and-dump would be my suggestion for
the best way to go.
73
Peter
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------------------------------
Date: Wed, 13 Oct 1999 22:43:37 +0200
From: "Paulus" <paulstra@xs4all.nl>
Subject: [psk31] Fw: [dsp] DSP-10 2 meter transceiver September/October QST
- ----- Oorspronkelijk bericht -----
Van: Dan Schultz <n8fgv@amsat.org>
Aan: TAPR DSP Special Interest Group <dsp@lists.tapr.org>
Verzonden: woensdag 13 oktober 1999 22:28
Onderwerp: [dsp] DSP-10 2 meter transceiver September/October QST
> I am gathering parts to build the 2 meter DSP transceiver that is
> described in the September and October QST. I already have about 10
> people interested in this project, so we should be able to buy the parts
> with some quantity price breaks. The bare PC boards are available for
> $45 and I estimate the cost of parts to populate the PCB is around $140.
> You will also need an Analog Devices EZ-Kit which is about $90, you can
> get 10% off of that from Newark Electronics web site until October 15.
>
> Please contact me at n8fgv@amsat.org before Friday if you want to go in
> on this order.
>
> Dan Schultz N8FGV
>
> ---
> You are currently subscribed to dsp as: PAULSTRA@XS4ALL.NL
> To unsubscribe send a blank email to leave-dsp-3028V@lists.tapr.org
>
>
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End of Psk31 Digest V1 #202
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