Date   

Re: Multiband loop dish feed

Daniel DL3IAE
 

Hi John,

there is a very detailed description of a multi-band loop feed from DD7MH, who also makes them.
One of the essentials is to keep the distance from the reflector constant - wavelenghts wise.

http://www.dd7mh.de/RingPraesentWeb/MehrbandRingstrWeb.html

It is in German but web translation should be good enough.
These feeds work very well for an f/D of around 0.4 to 0.5.
However, I would not recommend to use this type of feed for 5.7 and 10 GHz, unless you have a solid dish with sufficient accuracy.

Hope to work you on 9 cms next contest.
The conditions were crap on Saturday and not much better on Sunday.

73
Daniel
DL3IAE


Re: Octagon OSLG Green LNB

on4cjq@...
 

Hello Roger

Look at the Twitter page from PE1CMO, scroll dwn to 28 march 2019 and there you can see his mod for that lnb.

Best 73's

Jerry,ON4CJQ

----- Oorspronkelijk bericht -----
Van: "R Hopkins via groups.io" <gw4nos=btinternet.com@groups.io>
Aan: "UKMicrowaves" <UKMicrowaves@groups.io>
Verzonden: Maandag 8 maart 2021 17:07:30
Onderwerp: [UKMicrowaves] Octagon OSLG Green LNB

I've just bought an LNB marked:-

Single Octagon OSLG Green LNB

It was sold as having:-

PLL Technology 25MHz Crystal.

I'm having my doubts whether this is a PLL LNB because it wanders far more than others that I've
bought. I don't want to dismantle it at the moment. The advert was pretty specific about the 25MHz
Xtal.

So does anybody had experience of this particular LNB?

If it is a PLL LNB has anybody modified one for an external clock?

I've modified a number of LNBs over the years so that's not a problem. Just looking for a bit of
input from those who may know.

Roger GW4NOS


Re: Octagon OSLG Green LNB

John Fell
 

They do say it's 25MHz and PLL in the ads -maybe this one has a wobbly Xtal ?
Usual injection to one side of Xtal via a C should work .

73
John
G0API

On Mon, 8 Mar 2021 at 16:07, R Hopkins via groups.io <gw4nos=btinternet.com@groups.io> wrote:
I've just bought an LNB marked:-

Single Octagon OSLG Green LNB

It was sold as having:-

PLL Technology 25MHz Crystal.

I'm having my doubts whether this is a PLL LNB because it wanders far more than others that I've
bought. I don't want to dismantle it at the moment. The advert was pretty specific about the 25MHz
Xtal.

So does anybody had experience of this particular LNB?

If it is a PLL LNB has anybody modified one for an external clock?

I've modified a number of LNBs over the years so that's not a problem. Just looking for a bit of
input from those who may know.

Roger    GW4NOS







Re: Re GB3MCB

Dave
 

I have a suspicion that the fact that the beacon beams NNE using a sectoral horn meant that I wasn’t getting the maximum signal available. Needs more observation. 
73
Dave G4GLT. 


On 8 Mar 2021, at 15:55, John Fell <john.g0api@...> wrote:


Hi Dave ,
That signal is a good 579 in EME ears ......
I just looked up my last Spot of MCB and I see it is very close to the frequency you quote today - which makes me happy to know it was not another spurion .It was VERY weak though .Now my Pine tree 'tut West /SW is now 20Ft lower I hope to hear MCB during good RS .If all else may take some kit down to Helston in June hols .

73
John
G0API 

On Mon, 8 Mar 2021 at 13:05, Dave via groups.io <davidnewman55=icloud.com@groups.io> wrote:
I stopped briefly by the roadside at a very elevated spot 
(362 masl)at IO70XM west of Princetown with an excellent low horizon to the Cornish beacon on 10ghz.
The recording is enclosed , and I can convert it to another file type if necessary.
Using a DB6NT transverter mark 3 with GPS control and an FT817 the frequency came out at 10368.96833 MHz.
The report was 569 and with high pressure and only being 58km away I had expected thew beacon to be a bit stronger.
73
Dave G4GLT






Re: Multiband loop dish feed

John Lemay
 

Barry

 

You said < If you want to experiment, why not try a new feed with just the highest band loop by itself? >

 

Good idea – and one that I have already tried. The first three band loops I built were constructed in such a way as to make that test very awkward, but the current installation makes it relatively easy. With the 23 and 13cms loops removed, I was unable to detect any difference in performance of the 9cms loop. That was a pleasant surprise, but comes with the caveat of not being able to measure sun noise with as much precision as I would like. That is because my 9cms transverter is not particularly sensitive and is preceded by a bandpass filter (essential here due to LOS with TV transmitter). Such is the fun of amateur experiments !

 

Many thanks for your suggestions.

 

John G4ZTR

 

From: UKMicrowaves@groups.io [mailto:UKMicrowaves@groups.io] On Behalf Of Barry VE4MA
Sent: 08 March 2021 14:58
To: UKMicrowaves
Subject: [UKMicrowaves] Multiband loop dish feed

 

Hi John,

 

I have  not played with the loops, but with the dual dipoles over the ground plane, there is a dimiinishing return on the size of the groiund plane. A perfect ground plane gives you optimum gain for a reflector and does not keep giving additonal gain as a shaped reflector ( corner or parabolic ) would.

 

I suspect that the performance reduction on the highest band is probably due to the effect of the other loops on the pattern.    If you want to experiment, why not try a new feed with just the highest band loop by itself?

 

Best 73

Barry VE4MA


Virus-free. www.avg.com


Re: Multiband loop dish feed

Dave G6HEF
 

John,

I'll confess to being no expert, but one thing to consider is the dish accuracy. Referring to page 71 of The International Microwave Handbook 2nd Edition there is a graph. 1/10th wavelength deviation from a true parabola can give gain reduction of between 0.5 and 3.5db depending on the periodicity of the error. At 9cm 1/10 wavelength is 9mm and not very much. Any increase of error will obviously decrease gain. I'm not saying the feed can't be improved, but there will always be increasing gain reductions due to the wavelengths becoming significant compared to the overall dish error.

Dave
G6HEF


Re: 'MCB

Neil Smith G4DBN
 

KBQ has not been strong enough for a decode.  As usual, it's the old story that I can *see" it perfectly well on a long FFT integration, but JT4G is just too fast for it to have any hope of decoding. Tantalisingly close at times, and some very loud aircraft reflections, but conditions have been so absorptive that I can't even hear PKT, and (horror of horrors) failed to work a certain G4BAO the other day.

Funny to be moaning about not getting decodable signals from low power beacons 340 and 250 km away over obstructed paths on 10 GHz, just shows how far we've come since I first played on 3cm back in the 1970s.

Neil G4DBN

On 08/03/2021 15:47, John Fell wrote:


Have you had decodes from KBQ Neil ?


Octagon OSLG Green LNB

R Hopkins
 

I've just bought an LNB marked:-

Single Octagon OSLG Green LNB

It was sold as having:-

PLL Technology 25MHz Crystal.

I'm having my doubts whether this is a PLL LNB because it wanders far more than others that I've
bought. I don't want to dismantle it at the moment. The advert was pretty specific about the 25MHz
Xtal.

So does anybody had experience of this particular LNB?

If it is a PLL LNB has anybody modified one for an external clock?

I've modified a number of LNBs over the years so that's not a problem. Just looking for a bit of
input from those who may know.

Roger GW4NOS


Re: GB3MCB

John Fell
 

Very Fine !

73
John
G0API

On Mon, 8 Mar 2021 at 15:55, SAM JEWELL via groups.io <jewell=btinternet.com@groups.io> wrote:
My preference is towards the W/SW, based in location and windows in the room. 

73 de Sam


Sent tomorrow from my time machine


On 8 Mar 2021, at 15:49, John Fell <john.g0api@...> wrote:


Good to hear that Sam.
If it points out of a window looking SSW , I may be able to hear it again.

73
John
G0API

On Mon, 8 Mar 2021 at 14:26, SAM JEWELL via groups.io <jewell=btinternet.com@groups.io> wrote:
The subject of the GB3MHZ 3cm beacon came up during today’s Martlesham Radio Society AGM (on Zoom, where else?!).
The beacon power level is well down on normal, hence reception can be difficult. Site access is a continuing problem. However, as soon as room access can be arranged a temporary 3cm beacon, running a bit more power, will be installed in one of the tower windows. This will restrict take off direction, but is better than no beacon. Once outside access to the antenna gallery can be arranged, something more permanent can be installed.

73 de Sam, G4DDK


Sent tomorrow from my time machine


> On 8 Mar 2021, at 14:17, Chris Bartram G4DGU <chris@...> wrote:
>
> Was that report of the reception of 'MCB today, Dave? I'm located only about 5km from the beacon, and it is usually audible here, albeit quite weak due to the beacon's location not far up the mast on Hensbarrow Downs and path obstruction caused by the aforementioned lump of granite.
>
> On a near-LOS path, such as that from Hensbarrow to quite a lot of Dartmoor, the path losses can be quite low: as soon as obstructions come into play, they increase quite surprisingly.
>
> I've listened for the signal several times over the last few days, and nothing has been audible. Although I'm only using a low-noise feedhorn as an antenna, that has a waveguide-input HEMT preamp driving a transverter which is well proven, I'm surprised that I've not seen anything. If the output power has crashed significantly, that could explain the problem.
>
> One of the problems with MCB/10GHz is that the group who host it seem to give it a very low priority. I'm not even sure that they have the ability to monitor it properly. I get the impression that they treat it as a bit of a PITA.
>
> 73
>
> Chris G4DGU
>
>
>
>
>







Re: GB3MCB

SAM JEWELL
 

My preference is towards the W/SW, based in location and windows in the room. 

73 de Sam


Sent tomorrow from my time machine


On 8 Mar 2021, at 15:49, John Fell <john.g0api@...> wrote:


Good to hear that Sam.
If it points out of a window looking SSW , I may be able to hear it again.

73
John
G0API

On Mon, 8 Mar 2021 at 14:26, SAM JEWELL via groups.io <jewell=btinternet.com@groups.io> wrote:
The subject of the GB3MHZ 3cm beacon came up during today’s Martlesham Radio Society AGM (on Zoom, where else?!).
The beacon power level is well down on normal, hence reception can be difficult. Site access is a continuing problem. However, as soon as room access can be arranged a temporary 3cm beacon, running a bit more power, will be installed in one of the tower windows. This will restrict take off direction, but is better than no beacon. Once outside access to the antenna gallery can be arranged, something more permanent can be installed.

73 de Sam, G4DDK


Sent tomorrow from my time machine


> On 8 Mar 2021, at 14:17, Chris Bartram G4DGU <chris@...> wrote:
>
> Was that report of the reception of 'MCB today, Dave? I'm located only about 5km from the beacon, and it is usually audible here, albeit quite weak due to the beacon's location not far up the mast on Hensbarrow Downs and path obstruction caused by the aforementioned lump of granite.
>
> On a near-LOS path, such as that from Hensbarrow to quite a lot of Dartmoor, the path losses can be quite low: as soon as obstructions come into play, they increase quite surprisingly.
>
> I've listened for the signal several times over the last few days, and nothing has been audible. Although I'm only using a low-noise feedhorn as an antenna, that has a waveguide-input HEMT preamp driving a transverter which is well proven, I'm surprised that I've not seen anything. If the output power has crashed significantly, that could explain the problem.
>
> One of the problems with MCB/10GHz is that the group who host it seem to give it a very low priority. I'm not even sure that they have the ability to monitor it properly. I get the impression that they treat it as a bit of a PITA.
>
> 73
>
> Chris G4DGU
>
>
>
>
>







Re: Re GB3MCB

John Fell
 

Hi Dave ,
That signal is a good 579 in EME ears ......
I just looked up my last Spot of MCB and I see it is very close to the frequency you quote today - which makes me happy to know it was not another spurion .It was VERY weak though .Now my Pine tree 'tut West /SW is now 20Ft lower I hope to hear MCB during good RS .If all else may take some kit down to Helston in June hols .

73
John
G0API 

On Mon, 8 Mar 2021 at 13:05, Dave via groups.io <davidnewman55=icloud.com@groups.io> wrote:
I stopped briefly by the roadside at a very elevated spot 
(362 masl)at IO70XM west of Princetown with an excellent low horizon to the Cornish beacon on 10ghz.
The recording is enclosed , and I can convert it to another file type if necessary.
Using a DB6NT transverter mark 3 with GPS control and an FT817 the frequency came out at 10368.96833 MHz.
The report was 569 and with high pressure and only being 58km away I had expected thew beacon to be a bit stronger.
73
Dave G4GLT






Re: GB3MCB

John Fell
 

Good to hear that Sam.
If it points out of a window looking SSW , I may be able to hear it again.

73
John
G0API

On Mon, 8 Mar 2021 at 14:26, SAM JEWELL via groups.io <jewell=btinternet.com@groups.io> wrote:
The subject of the GB3MHZ 3cm beacon came up during today’s Martlesham Radio Society AGM (on Zoom, where else?!).
The beacon power level is well down on normal, hence reception can be difficult. Site access is a continuing problem. However, as soon as room access can be arranged a temporary 3cm beacon, running a bit more power, will be installed in one of the tower windows. This will restrict take off direction, but is better than no beacon. Once outside access to the antenna gallery can be arranged, something more permanent can be installed.

73 de Sam, G4DDK


Sent tomorrow from my time machine


> On 8 Mar 2021, at 14:17, Chris Bartram G4DGU <chris@...> wrote:
>
> Was that report of the reception of 'MCB today, Dave? I'm located only about 5km from the beacon, and it is usually audible here, albeit quite weak due to the beacon's location not far up the mast on Hensbarrow Downs and path obstruction caused by the aforementioned lump of granite.
>
> On a near-LOS path, such as that from Hensbarrow to quite a lot of Dartmoor, the path losses can be quite low: as soon as obstructions come into play, they increase quite surprisingly.
>
> I've listened for the signal several times over the last few days, and nothing has been audible. Although I'm only using a low-noise feedhorn as an antenna, that has a waveguide-input HEMT preamp driving a transverter which is well proven, I'm surprised that I've not seen anything. If the output power has crashed significantly, that could explain the problem.
>
> One of the problems with MCB/10GHz is that the group who host it seem to give it a very low priority. I'm not even sure that they have the ability to monitor it properly. I get the impression that they treat it as a bit of a PITA.
>
> 73
>
> Chris G4DGU
>
>
>
>
>







Re: 'MCB

John Fell
 

Maybe the spurious signal is due to a rusty bolt diode multiplier on the Wind machine ....LOL.

I think the Cornish Beacon Group do a good job of keeping beacons across the bands going and they are to be congratulated on providing space for a10GHz beacon .

My understanding is John G8ACE and Brian G4NNS provide the beacon and logistical support - from over 200 miles away .....

If MCB is to be heard it will probably be by RS and looking at forecast could occur quite soon .

Even LEX was below noise earlier today .

Have you had decodes from KBQ Neil ?

73
John
G0API


On Mon, 8 Mar 2021 at 14:59, Neil Smith G4DBN <neil@...> wrote:
Thanks Dave and Chris, what I was seeing is very very close to that
frequency, but I was definitely not seeing any FSK, so that nails the
factr that I was seeing something that is probably an artefact from a
strong out of band signal in the same direction. I can't see ANYTHING
that is in that direction though, so perhaps it is something on a
sidelobe, but I can't find it now.  Has to be on an X band or higher
frequency as the signal traverses 80cm of WR90.  There is nothing at all
in terms of human habitation or anothing other than fields for almost 15
miles, and then it is only a couple of villages.  There is a wind
tuirbine exactly on that path, so it is possible that I'm seeing a
reflection of a harmonic of something, but it is remarkably stable.

Anyway, definitely NOT GB3MCB. It would be great to see it again, I used
to see it coming through quite regularly.

Neil G4DBN


On 08/03/2021 14:46, Chris Bartram G4DGU wrote:
> Armed with Dave's measurement of frequency, I had another look for
> MCB, this time using a reputedly 20dBi patch array antenna. It is
> there, but just too weak to copy the FSK aurally. As an estimate, the
> level here is of the order of 25dB below that I which was seeing when
> I last looked - but that was about 18months ago.
>
> I almost agree with the frequency Dave quotes. Also using a GPS
> referenced system, I made the frequency (at about 14.00)
> 10368.896832MHz. As the beacon isn't frequency locked that's pretty
> close ...
>
> 73







Re: Multiband loop dish feed

David Law
 

I think that's a fair idea. I'd be interested to see how that goes. 


Re: 'MCB

Neil Smith G4DBN
 

Thanks Dave and Chris, what I was seeing is very very close to that frequency, but I was definitely not seeing any FSK, so that nails the factr that I was seeing something that is probably an artefact from a strong out of band signal in the same direction. I can't see ANYTHING that is in that direction though, so perhaps it is something on a sidelobe, but I can't find it now.  Has to be on an X band or higher frequency as the signal traverses 80cm of WR90.  There is nothing at all in terms of human habitation or anothing other than fields for almost 15 miles, and then it is only a couple of villages.  There is a wind tuirbine exactly on that path, so it is possible that I'm seeing a reflection of a harmonic of something, but it is remarkably stable.

Anyway, definitely NOT GB3MCB. It would be great to see it again, I used to see it coming through quite regularly.

Neil G4DBN

On 08/03/2021 14:46, Chris Bartram G4DGU wrote:
Armed with Dave's measurement of frequency, I had another look for MCB, this time using a reputedly 20dBi patch array antenna. It is there, but just too weak to copy the FSK aurally. As an estimate, the level here is of the order of 25dB below that I which was seeing when I last looked - but that was about 18months ago.

I almost agree with the frequency Dave quotes. Also using a GPS referenced system, I made the frequency (at about 14.00) 10368.896832MHz. As the beacon isn't frequency locked that's pretty close ...

73


Multiband loop dish feed

Barry VE4MA
 

Hi John,

I have  not played with the loops, but with the dual dipoles over the ground plane, there is a dimiinishing return on the size of the groiund plane. A perfect ground plane gives you optimum gain for a reflector and does not keep giving additonal gain as a shaped reflector ( corner or parabolic ) would.

I suspect that the performance reduction on the highest band is probably due to the effect of the other loops on the pattern.    If you want to experiment, why not try a new feed with just the highest band loop by itself?

Best 73
Barry VE4MA


Re: GB3MCB

Dave
 

Yes, GB3MCB was received this morning about 1100z. When I can listen properly I shall have to see if it can get a better signal level as it ought to be stronger I would have thought.
Dave G4GLT.

On 8 Mar 2021, at 14:26, SAM JEWELL via groups.io <jewell=btinternet.com@groups.io> wrote:

The subject of the GB3MHZ 3cm beacon came up during today’s Martlesham Radio Society AGM (on Zoom, where else?!).
The beacon power level is well down on normal, hence reception can be difficult. Site access is a continuing problem. However, as soon as room access can be arranged a temporary 3cm beacon, running a bit more power, will be installed in one of the tower windows. This will restrict take off direction, but is better than no beacon. Once outside access to the antenna gallery can be arranged, something more permanent can be installed.

73 de Sam, G4DDK


Sent tomorrow from my time machine


On 8 Mar 2021, at 14:17, Chris Bartram G4DGU <chris@chris-bartram.co.uk> wrote:

Was that report of the reception of 'MCB today, Dave? I'm located only about 5km from the beacon, and it is usually audible here, albeit quite weak due to the beacon's location not far up the mast on Hensbarrow Downs and path obstruction caused by the aforementioned lump of granite.

On a near-LOS path, such as that from Hensbarrow to quite a lot of Dartmoor, the path losses can be quite low: as soon as obstructions come into play, they increase quite surprisingly.

I've listened for the signal several times over the last few days, and nothing has been audible. Although I'm only using a low-noise feedhorn as an antenna, that has a waveguide-input HEMT preamp driving a transverter which is well proven, I'm surprised that I've not seen anything. If the output power has crashed significantly, that could explain the problem.

One of the problems with MCB/10GHz is that the group who host it seem to give it a very low priority. I'm not even sure that they have the ability to monitor it properly. I get the impression that they treat it as a bit of a PITA.

73

Chris G4DGU









'MCB

Chris Bartram G4DGU
 

Armed with Dave's measurement of frequency, I had another look for MCB, this time using a reputedly 20dBi patch array antenna. It is there, but just too weak to copy the FSK aurally. As an estimate, the level here is of the order of 25dB below that I which was seeing when I last looked - but that was about 18months ago.

I almost agree with the frequency Dave quotes. Also using a GPS referenced system, I made the frequency (at about 14.00) 10368.896832MHz. As the beacon isn't frequency locked that's pretty close ...

73

Chris G4DGU


Re: GB3MCB

SAM JEWELL
 

The subject of the GB3MHZ 3cm beacon came up during today’s Martlesham Radio Society AGM (on Zoom, where else?!).
The beacon power level is well down on normal, hence reception can be difficult. Site access is a continuing problem. However, as soon as room access can be arranged a temporary 3cm beacon, running a bit more power, will be installed in one of the tower windows. This will restrict take off direction, but is better than no beacon. Once outside access to the antenna gallery can be arranged, something more permanent can be installed.

73 de Sam, G4DDK


Sent tomorrow from my time machine

On 8 Mar 2021, at 14:17, Chris Bartram G4DGU <chris@chris-bartram.co.uk> wrote:

Was that report of the reception of 'MCB today, Dave? I'm located only about 5km from the beacon, and it is usually audible here, albeit quite weak due to the beacon's location not far up the mast on Hensbarrow Downs and path obstruction caused by the aforementioned lump of granite.

On a near-LOS path, such as that from Hensbarrow to quite a lot of Dartmoor, the path losses can be quite low: as soon as obstructions come into play, they increase quite surprisingly.

I've listened for the signal several times over the last few days, and nothing has been audible. Although I'm only using a low-noise feedhorn as an antenna, that has a waveguide-input HEMT preamp driving a transverter which is well proven, I'm surprised that I've not seen anything. If the output power has crashed significantly, that could explain the problem.

One of the problems with MCB/10GHz is that the group who host it seem to give it a very low priority. I'm not even sure that they have the ability to monitor it properly. I get the impression that they treat it as a bit of a PITA.

73

Chris G4DGU





Re: GB3MCB

Chris Bartram G4DGU
 

Was that report of the reception of 'MCB today, Dave? I'm located only about 5km from the beacon, and it is usually audible here, albeit quite weak due to the beacon's location not far up the mast on Hensbarrow Downs and path obstruction caused by the aforementioned lump of granite.

On a near-LOS path, such as that from Hensbarrow to quite a lot of Dartmoor, the path losses can be quite low: as soon as obstructions come into play, they increase quite surprisingly.

I've listened for the signal several times over the last few days, and nothing has been audible. Although I'm only using a low-noise feedhorn as an antenna, that has a waveguide-input HEMT preamp driving a transverter which is well proven, I'm surprised that I've not seen anything. If the output power has crashed significantly, that could explain the problem.

One of the problems with MCB/10GHz is that the group who host it seem to give it a very low priority. I'm not even sure that they have the ability to monitor it properly. I get the impression that they treat it as a bit of a PITA.

73

Chris G4DGU

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