Date   

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 <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


Re: How to decode JT4G #10ghz

Maarten PA0MHE
 

Found, thanks all


Re: How to decode JT4G #10ghz

Andy G4JNT
 

Use the up/down arrows on the Submode box.   Slightly bottom right of the centre


On Mon, 8 Mar 2021 at 10:44, Maarten PA0MHE <maarten.heuvelman@...> wrote:
Thanks Andy,

Sorry for my ignorance, but then my questions should be: How to select a "Submode"


Re: How to decode JT4G #10ghz

Tom GM8MJV
 

Maarten

Down by the ’Submode A’ field  there are two up/down arrows - click them.

This will list all the sub-mode - select G


Tom
GM8MJV

On 8 Mar 2021, at 10:44, Maarten PA0MHE <maarten.heuvelman@...> wrote:

Thanks Andy,

Sorry for my ignorance, but then my questions should be: How to select a "Submode"


Re: How to decode JT4G #10ghz

Maarten PA0MHE
 

Thanks Andy,

Sorry for my ignorance, but then my questions should be: How to select a "Submode"


Re: Phase Centre of WiFi dongle

John E. Beech
 

Very interesting Murray. Shows how much I'm out of touch with modern electronics. However, after googling how they
work, it seems the associated ground plane is doing a lot of the radiating & in a dongle the g-plane is probably acting
more like a patch antenna.
I might buy a few and try them as a dish feed.

de John G8SEQ

-------Original Message-------
From: Murray Niman <g6jyb@microwavers.org>
To: UKMicrowaves@groups.io <UKMicrowaves@groups.io>
Subject: Re: [UKMicrowaves] Phase Centre of WiFi dongle
Sent: Mar 08 '21 06:50

Plenty of small ceramic antennas around...
Look on here and you will see similar:-

https://uk.farnell.com/c/passive-components/antennas-single-band-chip

Their physical size vs freespace wavelength may not be uber-efficient
though, but for short range WiFi or bluetooth it doesnt matter much

Murray


Re: How to decode JT4G #10ghz

Andy G4JNT
 

I don't know what you mean by "JT4G A" indication

The mode is JT4, submodes A - G  
so you have JT4A, JT4B...JT4G.    The microwave beacons use JT4G

So just select G in the pulldown menu.

image.png


On Mon, 8 Mar 2021 at 09:07, Maarten PA0MHE <maarten.heuvelman@...> wrote:
The tick setting "Enable VHF and Submode Features" was already done. So does this mean WJST-X v2.4.0-rc1 now already can decode JT4G despite the JT4G A indication ?


Multiband loop dish feed

John Lemay
 

'Morning all

I have a question, and a proposal, about multiband loop dish feeds:

I'm using a home-made dish feed for 23/13/9cms, which is similar to the RF
HamDesign series, with a full wave circular loop for each band in front of a
140mm diameter solid reflector. Each band has a separate connector.

My gut feeling is that on 9cms, performance is down a few dB. I've measured
sun noise, which I found quite tricky, and there's a deficit of about 1.5dB
in the Y factor between sun and cold sky.

In terms of wavelengths, the reflector is a different size for each band.
Therefore on 9cms it is a relatively large reflector which leads to a
narrower beam from the feed, with consequent under illumination of the dish.
That's my thinking - and I'm happy to be corrected here !

Based on that thinking, my proposal is to use a solid reflector of about a
wavelength diameter on 9cms, surrounded by a mesh ring reflector of a
wavelength diameter on 23cms. For example, a 20mm mesh is almost transparent
at 9cms, but reflective on 23cms. This leaves a mid-way effectiveness on
13cms - not sure about this.

Is this proposal a totally whacky idea - or well worth trying ??

TIA

John G4ZTR


--
This email has been checked for viruses by AVG.
https://www.avg.com


Re: How to decode JT4G #10ghz

Maarten PA0MHE
 

The tick setting "Enable VHF and Submode Features" was already done. So does this mean WJST-X v2.4.0-rc1 now already can decode JT4G despite the JT4G A indication ?


Re: How to decode JT4G #10ghz

Maarten PA0MHE
 

Thanks Andy
73's Maarten


Re: How to decode JT4G #10ghz

Andy G4JNT
 

Go into  files-settings  and tick the box "Enable VHF and Submode Features"



On Mon, 8 Mar 2021 at 07:35, Maarten PA0MHE <maarten.heuvelman@...> wrote:
I'm trying to decode the GB3PKT beacon on 10GHz which I can receive weakly. However my WJST-X only knows JT4G-A.
Is there a difference and if Yes, how to setup decoding ?
--


How to decode JT4G #10ghz

Maarten PA0MHE
 

I'm trying to decode the GB3PKT beacon on 10GHz which I can receive weakly. However my WJST-X only knows JT4G-A.
Is there a difference and if Yes, how to setup decoding ?
--


Re: Phase Centre of WiFi dongle

Murray Niman
 


Plenty of small ceramic antennas around...
Look on here and you will see similar:-

https://uk.farnell.com/c/passive-components/antennas-single-band-chip

Their physical size vs freespace wavelength may not be uber-efficient though, but for short range WiFi or bluetooth it doesnt matter much

  Murray


Re: Phase Centre of WiFi dongle

Glyn M0XGT
 

I think it’s always going to be slightly tricky relying on the internal antenna in the dongle – better to either hack the board and connect via the test connector or use a device that has external antenna connectors. 
 
The solution I like is a Ubiquiti Bullet M5, or dual-chain Rocket M5, with external N-type or SMA (after RP-SMA adaptors) connectors and an Ethernet connection to a 24V POE switch or POE injector plus 24V DC-DC converter and LiPo. This lets you put the access point at the top of a mast with data and power run over a long outdoor Ethernet cable, and it leaves you with just a short coax run to the antenna ports. I get the ubiquity kit on eBay, new from Latvia or used from UK/EU.
 
I have a collection of different antennas depending on the task: 6 dBi or 8 dBi omnis for UAV ground-to-air links or general area coverage, a pair of 18 dBi patches for moderate distance, and a pair of 28 dBi dual-polarised dishes for much long point-to-point links. For short range links you can push the data-link channel bandwidth right up (300 Mb/s with 40 MHz channels, dual-chain) or dial it down to increase the range. 
 
Glyn M0XGT  
 

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