23cm FT* activity


David Ackrill
 

It's the EU digital modes (not just FT8, any MGM) on Wednesday 18th April 2022 from 17:00 to 21:00 UTC.

Will anyone be taking part again?  I'll have a look round the usual frequencies.

Dave (G0DJA)
IO93IF


SAM JEWELL
 

I'm planning to be on, circumstances permitting.

73 de Sam, G4DDK



On 16 May 2022, at 15:21, David Ackrill <david.ackrill@...> wrote:



It's the EU digital modes (not just FT8, any MGM) on Wednesday 18th April 2022 from 17:00 to 21:00 UTC.

Will anyone be taking part again?  I'll have a look round the usual frequencies.

Dave (G0DJA)
IO93IF


Barry Holloway
 

I’ll be on, Barry 2E0GTD
IO91GE18

What are the “usual” frequencies for FT* modes on 23cms?


On 16 May 2022, at 15:41, SAM JEWELL via groups.io <jewell@...> wrote:

I'm planning to be on, circumstances permitting.

73 de Sam, G4DDK



On 16 May 2022, at 15:21, David Ackrill <david.ackrill@...> wrote:



It's the EU digital modes (not just FT8, any MGM) on Wednesday 18th April 2022 from 17:00 to 21:00 UTC.

Will anyone be taking part again?  I'll have a look round the usual frequencies.

Dave (G0DJA)
IO93IF


David Ackrill
 

On Mon, May 16, 2022 at 10:13 AM, Barry Holloway wrote:
What are the “usual” frequencies for FT* modes on 23cms?

I usually start at 1296.174MHz for FT8, 1296.176MHz for FT4 and 1296.177MHz for Q65. After that, what ever agreement is made by making a sked.

I try to avoid the EME frequencies, even if the moon is nowhere near, just so as not to upset the EME enthusiasts.

Dave (G0DJA)

 


David Ackrill
 

I did better last night than in April. In April 1 contact, so 1 point times a multiplier of 1 = 1.

Last night, 5 contacts in 5 different squares, so 5 x 5 = 25 points.  3 were FT8, two were Q65. 4 different countries (Netherlands, England, Scotland and Northern Ireland).


SAM JEWELL
 

Running just 10W from the IC9700 and no masthead preamp I worked 6 stations. All but one in The Netherlands.

I conclude that multipath 'spreading' is a real problem with FT8 on 23cm. It was very noticeable that stations that were appearing with a wide signal and sounding distorted, were not always decoding. If I swung the beam just off a few degrees the signal cleaned up noticeably and successfully decoded each over. The multiple wind turbines off the Suffolk coast may be responsible for much of the multipath I experience. I discount aircraft reflection because there was little evidence of doppler on most of these signals.

Has anyone else noticed the same correlation between signal width and failed decoding?


73 de Sam, G4DDK




Andy G4JNT
 

That is why FT8 was designed for HF use, while Q65, with all the speed and tone spacing options you could want,  was designed for just such paths.



On Thu, 19 May 2022 at 11:48, SAM JEWELL via groups.io <jewell=btinternet.com@groups.io> wrote:
Running just 10W from the IC9700 and no masthead preamp I worked 6 stations. All but one in The Netherlands.

I conclude that multipath 'spreading' is a real problem with FT8 on 23cm. It was very noticeable that stations that were appearing with a wide signal and sounding distorted, were not always decoding. If I swung the beam just off a few degrees the signal cleaned up noticeably and successfully decoded each over. The multiple wind turbines off the Suffolk coast may be responsible for much of the multipath I experience. I discount aircraft reflection because there was little evidence of doppler on most of these signals.

Has anyone else noticed the same correlation between signal width and failed decoding?


73 de Sam, G4DDK




SAM JEWELL
 

Which is what I have been saying all along.

Not the most sensible mode for 23cm. I am amazed it works at all.......


Sam





------ Original Message ------
From: "Andy G4JNT" <andy.g4jnt@...>
To: UKMicrowaves@groups.io
Sent: Thursday, 19 May, 22 At 11:57
Subject: Re: [UKMicrowaves] 23cm FT* activity

That is why FT8 was designed for HF use, while Q65, with all the speed and tone spacing options you could want, was designed for just such paths.



On Thu, 19 May 2022 at 11:48, SAM JEWELL via groups.io <jewell=btinternet.com@groups.io> wrote:
Running just 10W from the IC9700 and no masthead preamp I worked 6 stations. All but one in The Netherlands.

I conclude that multipath 'spreading' is a real problem with FT8 on 23cm. It was very noticeable that stations that were appearing with a wide signal and sounding distorted, were not always decoding. If I swung the beam just off a few degrees the signal cleaned up noticeably and successfully decoded each over. The multiple wind turbines off the Suffolk coast may be responsible for much of the multipath I experience. I discount aircraft reflection because there was little evidence of doppler on most of these signals.

Has anyone else noticed the same correlation between signal width and failed decoding?


73 de Sam, G4DDK




Colin Ranson
 

Sam,

 

I am convinced that the windfarms out in the sea just off our coast are responsible for a lack of temperature inversion ducting these days. 2m and 70cm especially.   Remember when there used to lots of it ?

 

See you next LSB

 

 

Colin de G8LBS.

 

Sent from Mail for Windows

 

From: SAM JEWELL via groups.io
Sent: 19 May 2022 11:48
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] 23cm FT* activity

 

Running just 10W from the IC9700 and no masthead preamp I worked 6 stations. All but one in The Netherlands.

I conclude that multipath 'spreading' is a real problem with FT8 on 23cm. It was very noticeable that stations that were appearing with a wide signal and sounding distorted, were not always decoding. If I swung the beam just off a few degrees the signal cleaned up noticeably and successfully decoded each over. The multiple wind turbines off the Suffolk coast may be responsible for much of the multipath I experience. I discount aircraft reflection because there was little evidence of doppler on most of these signals.

Has anyone else noticed the same correlation between signal width and failed decoding?

 

73 de Sam, G4DDK

 

 

 


Mike Willis
 

Really? Interested in the science behand that conclusion.

Turbulence is what causes troposcatter. A windfarm might disturb the local evaporation duct but only in a specific direction. It's unlikely to impact other types of ducting. Scatter off the blades might raise signals a bit, especially if they are metallic. The vortexes might enhance troposcatter but probably limited as there are so few of them relatively speaking to other mechanisms creating turbulence.

The major reason for poorer propagation might be most people these days are deaf due to local noise. That and climate change to weather systems maybe.
--
Mike G0MJW


SAM JEWELL
 

There I respectfully disagree. I see as much ducting as ever (judging by the Belgian radar strength and beacons).
There is less random activity from amateurs on the near continent and this may give the impression of poorer, infrequent, conditions. Sea ducting  (maritime region) doesn't extend more than about 30-40km inland according to the COST 210 report (depends on coastal topography). Many of the nearer continental beacons are within that region and they are as frequently heard as ever. 
The wind generators do cause some odd sounding signals, both as back reflections from Martlesham and other UK beacons and as a form of modulation on some continental signals. 
The Belgian 23cm radar seems to illuminate a vast number of the generators, as it rotates, leading to almost continuous 'buzzing' when sea ducting is very strong. Tuesday night, during the UKAC/NAC contest, the buzzing made the band almost impossible to use when beaming roughly SE from here. Noise blankers don't deal too effectively with this type of noise!

73 de Sam





On 19 May 2022, at 13:04, Colin Ranson <g8lbs@...> wrote:



Sam,

 

I am convinced that the windfarms out in the sea just off our coast are responsible for a lack of temperature inversion ducting these days. 2m and 70cm especially.   Remember when there used to lots of it ?

 

See you next LSB

 

 

Colin de G8LBS.

 

Sent from Mail for Windows

 

From: SAM JEWELL via groups.io
Sent: 19 May 2022 11:48
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] 23cm FT* activity

 

Running just 10W from the IC9700 and no masthead preamp I worked 6 stations. All but one in The Netherlands.

I conclude that multipath 'spreading' is a real problem with FT8 on 23cm. It was very noticeable that stations that were appearing with a wide signal and sounding distorted, were not always decoding. If I swung the beam just off a few degrees the signal cleaned up noticeably and successfully decoded each over. The multiple wind turbines off the Suffolk coast may be responsible for much of the multipath I experience. I discount aircraft reflection because there was little evidence of doppler on most of these signals.

Has anyone else noticed the same correlation between signal width and failed decoding?

 

73 de Sam, G4DDK

 

 

 


Nigel G8IFN
 

I must be the "but one" that Sam worked.
I worked 9 stations in six squares, 2 in the UK, 6 in the Netherlands and 1 in Belgium using IC-9700 into 16ele in the loft fixed pointing roughly SE.
It may not be the ideal data mode for the higher frequency bands but I had nine more contacts on 23cm than I would normally have on a Wednesday evening.
--
Nigel G8IFN - JO01LS


David Ackrill
 

On Thu, May 19, 2022 at 04:20 AM, SAM JEWELL wrote:
Not the most sensible mode for 23cm. I am amazed it works at all.......

It's interesting to compare the performance of different modes of communication though.  I see both the double reflection, two or more additional traces that run in parallel with the main transmission, and the aircraft scattered version, where the additional traces either converge with or diverge from the main transmission.  The aircraft one seems to be worst for not getting a decode when using FT8.

I've not yet worked out how much 'Max Drift' to set when using Q65 on 23cm though.  Has anyone played with that setting and have any advice?