[pskmail] Re: pskmail on other mode

  • From: John Douyere <vk2eta@xxxxxxxxx>
  • To: pskmail@xxxxxxxxxxxxx
  • Date: Fri, 28 Aug 2009 07:57:57 +1000

Hi Greg,

Here in VK we have long distances and not many people in between, so mobile
coverage is quickly fading off when we get away from the cities.

So I have done a number of experiments in HF NVIS and VHF and although it is
not "PSKmail" per say it works quite well with other modes (some better than
others).

Here is a summary of my experience:

- in VHF and UHF I did some comparisons between SSB and FM. Although FM
needs a higher signal to noise ratio than SSB to work for voice, some
digital modes give almost the same performance in SSB and FM: I have tried
successfully THOR, MFSK but not DominoEX for a strange reason.

One issue with SSB on VHF and worse in UHF is that for staying within the
acquisition range of the server (typically 20 to 40Hz), the accuracy of the
VFO would need to be much higher than what is available currently. My FT857
and 817 give at best +/-1PPM but at 145MHZ I would need 0.27PPM of
stability.

So most modes like PSK, and the slow MFSK ones are difficult to tune using
SSB at VHF as it is easy to be 100 or 150Hz out despite having the right
dial frequency.

This is where FM wins, because tuning is not so important. So what you loose
in sensitivity (a little only with the right modes), you gain in ease of
tuning. The only modes I had success with on VHF/SSB was THOR because of
it's tolerance to mis-tuning.

Using FM, I could barely hear the signal in the noise (no squelch), but the
decoding was good. In only one case did THOR perform better on SSB than on
FM.

- In HF, as Rein (or Per I am not sure) has confirmed by tests, some other
modes are much more sensitive than PSK250 or 125. They also survive much
better the multipath distorsion of NVIS and lightning strikes noise in the
low frequencies (typically 80 and 40M).

My best experiences have been using MFSK and THOR. I had poor results with
DominoEX which is strange since it is a close cousin of THOR. I also had
poor results with the MT modes because I believe of the interaction between
fldigi and PSKMail (the control characters are not consistently passed
through in my experience).

I haven't tried Olivia much but it should work also.

So my best vote so far based on my experience: THOR8 for robustness (but it
is slow), otherwise THOR22 is a good compromise. For speed MFSK64 is really
good but 1K bandwidth, and MFSK16 or 22 a good compromise between robustness
and bandwidth.

In my experience in marginal conditions THOR22 and MFSK32 will beat PSK
hands down. You can try one of these two with the current settings in the
servers.

Note that if you want to use the slower modes like THOR8 or MFSK16 some
adjustments to the timings of the server are necessary. In fact I have
compiled a series of small changes that are required for the server to
accept these slow modes.

I can now successfully have a position report or a connected session with
THOR8. I get a very very robust link. I can send you the code if you want to
experiment.

Sorry for the long response, but I find that subject interesting.

Hope this helps,

Regards,

 John (VK2ETA)


On Fri, Aug 28, 2009 at 5:11 AM, Greg <kb1ncj@xxxxxxxxx> wrote:

> Would pskmail function on MT63 2k on vhf, uhf? It wouldn't be "psk"mail,
> but was wanting to experiment...   -Greg
>
>

Other related posts: