Re: 10GHz World Record


Richard GD8EXI
 

Marcus
Thank you for the information.
The last time I tried contacting EA8 on 1296MHz was indeed during the opening of the 3rd Sept 2013 as reported in Radcom.
On 144 and 432MHz I was running 400 watts at the antenna with 15.0 and 18.4dBd of antenna gain respectively. On 1296MHz at that time I was running about 300 watts at the antenna with 18.8dBd of antenna gain, so the three stations were quite similar in terms of erp.
 
I am afraid I did not take notes as to the equipment at the other end however I do remember the stations were running a lot less power on 1296MHz so I was expecting a possible one way contact using 70cms for talk back but it did not happen. The reports on 432MHz were in the 4.2 to 5.5 range so quite weak. So it could just be that the 1296MHz signals were below the threshold because of poor coupling into the duct as you said.
 
I am indeed at 60metres ASL and with the ground rising to 160metres 3Kms away on the bearing of 203 deg to EA8. So far from an ideal take off at this end probably causing significant extra loss.
 
My general observation is that the sea paths to EA8 or NW mainland Spain do tend to show a marked frequency dependence in contrast to the tropo path to HB9 where I can often move up band by band to 1296MHz with similar reports on each band.
 
Recent examples being 30/12/2014 and 5/1/2015 when I had 13 QSOs on 144 and 432MHz over 1000Kms to SW France and Northern Spain but no successful QSYs up to 1296MHz.
 
This is just anecdotal evidence and what is needed is a systematic study of beacon strengths across the different band over a long period.
 
With the advent SDR receivers it should be possible to monitor multiple beacon frequencies logging the signal to noise ratio against time. Has anybody tried this or know of any software to do it?
 
 
73s
Richard
GD8EXI



On 14/01/2015 20:06, "marcuswalden@... [ukmicrowaves]" <ukmicrowaves@...> wrote:

 
 
 
   

Richard,
 
Assuming that you are talking about 3 September 2013 (VHF/UHF column in RadCom November 2013), I looked at some radiosonde data at 1200 UTC for this date.
 
There was an elevated duct over Camborne (UK) with its top at ~770 m and a depth of ~350 m that might support frequencies down to ~37 MHz. Above Funchal (Madeira), the elevated duct top was at ~640 m with a depth of ~140 m, while above Guimar (Tenerife) the top was at ~950 m and its depth was ~600 m.
 
From this radiosonde data, one might assume that there was a continuous elevated duct extending from the UK to the Canary Islands, albeit one where the characteristics changed with distance.


Weather charts for this time period indicate a high pressure system over the Bay of Biscay, which suggests the elevated duct was a subsidence duct.

 
I believe your station is at ~60 m altitude so there would have been a sizeable coupling loss into the elevated duct (~60 dB?). There might have been sufficient link budget to establish a contact on 430 MHz but the additional loss at 1296 MHz could just have been too much.


How do the conducted powers and antenna gains for your system compare at 430 MHz and 1296 MHz?


Do you know the station details at the other end of the link?

If you and/or ! the other station had been closer to or within the duct, the coupling losses would have been much lower. I wonder if you then might also have established the contact at 1296 MHz or even higher frequencies. Obviously, there are physical/practical limitations to getting the station higher to take advantage of these elevated ducts.
Hope this is of interest.
 
Marcus G0IJZ

 
   


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