Date   

Re: Feed horn drain hole

Dominique Dehays
 

Hi all,

Just use extruded polystyrene (styrodur) , u can find in any supplier, it's cheap and easy to glue.
I use it on all my horns up to 47GHz.There is no influence on RF.Sun noise measurement validated.
73
Dom


-------- Message d'origine --------
De : g4cch_1 <g4cch_1@...>
Date : 16/05/2020 13:12 (GMT+01:00)
À : UKMicrowaves@groups.io
Objet : Re: [UKMicrowaves] Feed horn drain hole

You might try sticking Kapton tape over the mouth of the feed to stop rain getting into the horn. Apparently this is ok at 3cm. CT1BYM and few others are using it


Re: Feed horn drain hole

g4cch_1
 

You might try sticking Kapton tape over the mouth of the feed to stop rain getting into the horn. Apparently this is ok at 3cm. CT1BYM and few others are using it


Re: Speaking of MOQs

Bo, OZ2M
 

You can buy M-C devices from Mouser without any MOQ requirement - but, you have to be in the Americas :-( So if you can find a solution to the latter it may be the way forward.

Bo


Re: yet more fibre-glass dishes

John E. Beech
 

Hi agn Brian,
A couple of queries. Looking closely at the photos, in the second & third one I can just about make out the 45 deg wires at 8 mm separation. What is more obvious is are the horizontal wires/metalisation in two halves either side of the vertical centre line. They look to be about one wavelength apart at 10 GHz. What do they do?
Are they part of the polarization rotating mechanism or are they something to do with beam formation? Are there any wires in the supporting cone? ( I just used a tripod arrangement as my secondary reflector support.)

de John G8SEQ

-------Original Message-------
From: Brian Howie GM4DIJ <brian@b-howie.co.uk>
To: UKMicrowaves@groups.io <UKMicrowaves@groups.io>
Subject: [UKMicrowaves] yet more fibre-glass dishes
Sent: May 15 '20 20:19


All this talk of fibre glass dishes prompted me to look at mine.

I use a fibre glass  Cassegrain dish on 3cm . It's an ex Ferranti Blue
Parrot  monopulse radar dish. Tom Holbert GM3DXJ, who did much to
promote 3cm activity in Scotland was able to obtain a number of such
scrapped dishes in the early 1970s. I think it's about 2ft diameter

There's a description here

http://www.lothiansradiosociety.com/lrs-archive/50-photographs-early-year
s/766-1972-gm4dij-portable-3cm-operations>

"The Cassegrain configuration is quite clever. The dish consists of an
array of wires at 45 deg, and the secondary reflector, horizontal wires.
Horizontally polarised incoming signals pass through the secondary
reflector but are rotated to vertical polarisation by the dish and then
can be reflected by the secondary reflector onto the horn feed. This
largely removes the aperture loss caused by the reflector"

If you look at the photographs, the dish is almost transparent. There
was some metalisation on the back but it's almost gone on mine.

Of course this dish will only work near 10GHz , but it's an extremely
light weight dish. The wires are very thin and are spaced about 8mm on
the front surface of the parabola. On the curved sub-reflector, the
wires are about 2mm apart.

I've never seen a description of how well this scheme works.

If you scaled it to 23cm, the wires would be about 60mm apart and 15mm
respectively. Anyone fancy a go ?

Brian GM4DIJ


--
Brian Howie

--
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus





Re: yet more fibre-glass dishes

John E. Beech
 

Hi Brian,
I made a 10 GHz Cassegrain feed for a 60 cm dish many years ago. The subreflector has to be a hyperbolic curve. The first one I made was out of fibre glass, but I got the calculations wrong - it was too curved. When I realized how shallow the curve should be I just bashed a large ( catering size) coffee tin lid into shape with a ball pein & rubber hammers like panel beaters use. The dish was aluminium ( Ive still got the dish). The system effectively makes the f/D ratio bigger so I was able to use a 3 dB horn feed. I never did use it in anger, only did tests down the garden to confirm the beam width against calculations.

de John G8SEQ

-------Original Message-------
From: Brian Howie GM4DIJ <brian@b-howie.co.uk>
To: UKMicrowaves@groups.io <UKMicrowaves@groups.io>
Subject: [UKMicrowaves] yet more fibre-glass dishes
Sent: May 15 '20 20:19


All this talk of fibre glass dishes prompted me to look at mine.

I use a fibre glass  Cassegrain dish on 3cm . It's an ex Ferranti Blue
Parrot  monopulse radar dish. Tom Holbert GM3DXJ, who did much to
promote 3cm activity in Scotland was able to obtain a number of such
scrapped dishes in the early 1970s. I think it's about 2ft diameter

There's a description here

http://www.lothiansradiosociety.com/lrs-archive/50-photographs-early-year
s/766-1972-gm4dij-portable-3cm-operations>

"The Cassegrain configuration is quite clever. The dish consists of an
array of wires at 45 deg, and the secondary reflector, horizontal wires.
Horizontally polarised incoming signals pass through the secondary
reflector but are rotated to vertical polarisation by the dish and then
can be reflected by the secondary reflector onto the horn feed. This
largely removes the aperture loss caused by the reflector"

If you look at the photographs, the dish is almost transparent. There
was some metalisation on the back but it's almost gone on mine.

Of course this dish will only work near 10GHz , but it's an extremely
light weight dish. The wires are very thin and are spaced about 8mm on
the front surface of the parabola. On the curved sub-reflector, the
wires are about 2mm apart.

I've never seen a description of how well this scheme works.

If you scaled it to 23cm, the wires would be about 60mm apart and 15mm
respectively. Anyone fancy a go ?

Brian GM4DIJ


--
Brian Howie

--
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus





Re: Feed horn drain hole

Steve G4HTZ
 

Hi john 
be interested to hear how you get on as I have the same feed ...still in it’s delivery box !!
still getting round to boxing up the new 10ghz transverter 
--
Steve G4HTZ 
JO01JN

23cms 350w to 36 element 
10ghz 12w 80cm dish 
24ghz 1.8w 80cm dish 

currently not active due to house move 


yet more fibre-glass dishes

Brian Howie GM4DIJ
 

All this talk of fibre glass dishes prompted me to look at mine.

I use a fibre glass Cassegrain dish on 3cm . It's an ex Ferranti Blue Parrot monopulse radar dish. Tom Holbert GM3DXJ, who did much to promote 3cm activity in Scotland was able to obtain a number of such scrapped dishes in the early 1970s. I think it's about 2ft diameter

There's a description here

http://www.lothiansradiosociety.com/lrs-archive/50-photographs-early-year
s/766-1972-gm4dij-portable-3cm-operations>

"The Cassegrain configuration is quite clever. The dish consists of an array of wires at 45 deg, and the secondary reflector, horizontal wires. Horizontally polarised incoming signals pass through the secondary reflector but are rotated to vertical polarisation by the dish and then can be reflected by the secondary reflector onto the horn feed. This largely removes the aperture loss caused by the reflector"

If you look at the photographs, the dish is almost transparent. There was some metalisation on the back but it's almost gone on mine.

Of course this dish will only work near 10GHz , but it's an extremely light weight dish. The wires are very thin and are spaced about 8mm on the front surface of the parabola. On the curved sub-reflector, the wires are about 2mm apart.

I've never seen a description of how well this scheme works.

If you scaled it to 23cm, the wires would be about 60mm apart and 15mm respectively. Anyone fancy a go ?

Brian GM4DIJ


--
Brian Howie

--
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus


Feed horn drain hole

John Lemay
 

One of my (many) lockdown projects is to revisit an offset dish and feed for
3cms. I'm hoping for a chance to make a direct comparison with my current PF
dish. I have at last got my head around the geometry !

One possible arrangement of the dish and feed will result in the feed
pointing up at an angle, making it liable to fill with water when it rains.
Covering the aperture is possible but I feel that a drain hole would be a
good idea. The feed I have is from I0LVA, and the feed point is an SMA
socket into a waveguide sized cavity with a sealed end. It's the linear feed
here :- http://www.i0lva.it/foto.html

Where can I put a drain hole, which will not compromise the RF performance ?

Thanks

John G4ZTR


Re: MGF 1200 & chipbank items.

John E. Beech
 

OK Mike,
It will be Monday before I do anything. We are both fine. Cycling mainly for exercise, with some countryside walks & digging the allotment. Sadly no sailing yet. I'm hoping to go fishing next week - that way I get to talk to some non-amateur friends albeit at a distance.

de John G8SEQ

-------Original Message-------
From: Michael Scott via groups.io <g3lyp=btinternet.com@groups.io>
To: UKMicrowaves@groups.io <UKMicrowaves@groups.io>
Subject: Re: [UKMicrowaves] MGF 1200 & chipbank items.
Sent: May 15 '20 15:33

Hi John

That is very kind of you, I would be pleased to have them and will include
them in the next catalogue update. If you don't want to visit the post
office, I found that you can print a prepaid label online on the Royal Mail
website and if you can find one of the post boxes which accepts parcels, you
can post them without any human contact!
I did this when I was posting out the LDMOS amplifiers recently. The parcel
boxes tend to be located in or near industrial estates. I haven't looked,
but there may be a location guide on the website.

Hope you are keeping well, we are both OK.

73, Mike.

-----Original Message-----
From: John E. Beech
Sent: Friday, May 15, 2020 3:04 PM
To: UKMicrowaves@groups.io
Subject: [UKMicrowaves] MGF 1200 & chipbank items.

Hi Mike,
           Tnx for the MGF 1200's. They arrived 2 days ago but I've only
just had chance to open the packet! Other things got in the way like broken
seat belt stalk in my car.
            I've found my excess SM stock. They are on 7" reels, all nearly
full, so god knows how many thousands.
THEY ARE ALL 1206 PACKAGES In no particular order they are:

Part numbers: BAV70 switching diodes
                    Capacitors type C1206J Value 150 ? (pF?) Tolerance J
Voltage 50
                     BZX84 -C7v5 Zener diodes
                    Capacitors 1206J0500333JX-c09 2500 on reel!
                    CHIP CAP  12062B223K9AB Mullard
                     BZX84C3V9 ZENER DIODE
                     CAPACITOR 100N 50 V
                     ANOTHER REEL OF C3V9 ZENERS 3000 PPI
                     CAPACITOR 100000 pF + OR - 20%  qty 3000
                     CAPACITORS 22N 50V QTY 2 x 2500 REELS
                     CAPACITORS 22N 50 V 105 TOL. 3000

IF YOU WANT THEM FOR THE CHIP BANK I'LL BOX THEM UP AND POST THEM FOC.

I'll take a couple of hundred off each reel for my own use. I seem to
remember having some electrolytics about 8 mm long but they seem to have
disappeared.

There is also a polybag of about a hundred 100pF 100v 10% caps., but I'll
hang onto those, unless anyone is in desperate need of some.

de John G8SEQ








Re: MGF 1200 & chipbank items.

Michael Scott
 

Hi John

That is very kind of you, I would be pleased to have them and will include them in the next catalogue update. If you don't want to visit the post office, I found that you can print a prepaid label online on the Royal Mail website and if you can find one of the post boxes which accepts parcels, you can post them without any human contact!
I did this when I was posting out the LDMOS amplifiers recently. The parcel boxes tend to be located in or near industrial estates. I haven't looked, but there may be a location guide on the website.

Hope you are keeping well, we are both OK.

73, Mike.

-----Original Message-----
From: John E. Beech
Sent: Friday, May 15, 2020 3:04 PM
To: UKMicrowaves@groups.io
Subject: [UKMicrowaves] MGF 1200 & chipbank items.

Hi Mike,
Tnx for the MGF 1200's. They arrived 2 days ago but I've only just had chance to open the packet! Other things got in the way like broken seat belt stalk in my car.
I've found my excess SM stock. They are on 7" reels, all nearly full, so god knows how many thousands.
THEY ARE ALL 1206 PACKAGES In no particular order they are:

Part numbers: BAV70 switching diodes
Capacitors type C1206J Value 150 ? (pF?) Tolerance J Voltage 50
BZX84 -C7v5 Zener diodes
Capacitors 1206J0500333JX-c09 2500 on reel!
CHIP CAP 12062B223K9AB Mullard
BZX84C3V9 ZENER DIODE
CAPACITOR 100N 50 V
ANOTHER REEL OF C3V9 ZENERS 3000 PPI
CAPACITOR 100000 pF + OR - 20% qty 3000
CAPACITORS 22N 50V QTY 2 x 2500 REELS
CAPACITORS 22N 50 V 105 TOL. 3000

IF YOU WANT THEM FOR THE CHIP BANK I'LL BOX THEM UP AND POST THEM FOC.

I'll take a couple of hundred off each reel for my own use. I seem to remember having some electrolytics about 8 mm long but they seem to have disappeared.

There is also a polybag of about a hundred 100pF 100v 10% caps., but I'll hang onto those, unless anyone is in desperate need of some.

de John G8SEQ


MGF 1200 & chipbank items.

John E. Beech
 

Hi Mike,
Tnx for the MGF 1200's. They arrived 2 days ago but I've only just had chance to open the packet! Other things got in the way like broken seat belt stalk in my car.
I've found my excess SM stock. They are on 7" reels, all nearly full, so god knows how many thousands.
THEY ARE ALL 1206 PACKAGES In no particular order they are:

Part numbers: BAV70 switching diodes
Capacitors type C1206J Value 150 ? (pF?) Tolerance J Voltage 50
BZX84 -C7v5 Zener diodes
Capacitors 1206J0500333JX-c09 2500 on reel!
CHIP CAP 12062B223K9AB Mullard
BZX84C3V9 ZENER DIODE
CAPACITOR 100N 50 V
ANOTHER REEL OF C3V9 ZENERS 3000 PPI
CAPACITOR 100000 pF + OR - 20% qty 3000
CAPACITORS 22N 50V QTY 2 x 2500 REELS
CAPACITORS 22N 50 V 105 TOL. 3000

IF YOU WANT THEM FOR THE CHIP BANK I'LL BOX THEM UP AND POST THEM FOC.

I'll take a couple of hundred off each reel for my own use. I seem to remember having some electrolytics about 8 mm long but they seem to have disappeared.

There is also a polybag of about a hundred 100pF 100v 10% caps., but I'll hang onto those, unless anyone is in desperate need of some.

de John G8SEQ


Re: N plug for RG401

Phil Guttridge G3TCU
 

Thanks Andy (and others who replied to this).

Keith GU6EFB was planning to put in an order to Mouser and he kindly offered to add the connector I wanted to his order. So I should be OK for this part.


I'll try Richard if I ever need another one. (Glad to know about his Health & Safety!)

73, Phil G3TCU



On 15/05/2020 14:40, G8VLL via groups.io wrote:
Hello Phil,
                 Try Richard G6HKS, he has genuine H & S


Regards

Andy
G8VLL

Virus-free. www.avg.com


Re: N plug for RG401

G8VLL
 

Hello Phil,
                 Try Richard G6HKS, he has genuine H & S


Regards

Andy
G8VLL


Offset Dishes - some important notes by K2RIW

Chris Bartram G4DGU
 

Further to the discussions of the last few days, I remembered that I had in my collection of papers and notes a couple of notes by K2RIW which I have found useful in the past. I thought to upload them to the files section of this Group, but then discovered that I'd already done so a few years ago! They are in the section called '

Dick Knadle became a silent key not so many days ago, and these contributions by him are a fitting way of remembering a man who through his writings taught many of us a great deal about microwaves, and associated subjects.

See: <https://groups.io/g/UKmicrowaves/files/Antennas/K2RIW Papers>

73

Chris

G4DGU


Re: Speaking of MOQs

Conrad, PA5Y
 

Thank you everybody, I'll have a go at this tonight when I get home from work. One very nice member of this group is sending me 4 devices but 3 more would give me a little more peace of mind.

Regards

Conrad PA5Y


From: UKMicrowaves@groups.io <UKMicrowaves@groups.io> on behalf of David Holman via groups.io <davidholman8183@...>
Sent: 15 May 2020 10:56
To: UKMicrowaves@groups.io <UKMicrowaves@groups.io>
Subject: Re: [UKMicrowaves] Speaking of MOQs
 

Hello Conrad.
EZ samples is the answer. On the 71MHz up Converter Page over on the BATC wiki I wrote:-
The Mini-Circuits Mixer and MMIC amplifiers are stocked by Mini-kitsalthough an email to Mini-Circuits sales in Surrey (sales@...) would be a best first approach and avoid paying import duty. Update:- Mini-circuits UK advised that applications for EZ Samples of the PGA103+ and ADE-11X+ are acceptable for home constructors. Register with the Mini-Circuits website. Go to the page for one of these parts then press the EZ sample button on the right, fill out the application, reasons and objectives form, add the second item, do the export declaration and press send. Free of charge components arrive a few days later! 

It’s very decent of Mini-circuits. I hope it works for you. 

73
David M0YDH


Re: Speaking of MOQs

David Holman
 

Hello Conrad.
EZ samples is the answer. On the 71MHz up Converter Page over on the BATC wiki I wrote:-
The Mini-Circuits Mixer and MMIC amplifiers are stocked by Mini-kitsalthough an email to Mini-Circuits sales in Surrey (sales@...) would be a best first approach and avoid paying import duty. Update:- Mini-circuits UK advised that applications for EZ Samples of the PGA103+ and ADE-11X+ are acceptable for home constructors. Register with the Mini-Circuits website. Go to the page for one of these parts then press the EZ sample button on the right, fill out the application, reasons and objectives form, add the second item, do the export declaration and press send. Free of charge components arrive a few days later! 

It’s very decent of Mini-circuits. I hope it works for you. 

73
David M0YDH


Re: Speaking of MOQs

Dave G8KHU
 

Hi Conrad, Andy

Mini-Circuits have had a shake-up in their sales policy a few years ago and the minimum number you could purchase of any individual part number increased. So now if you want 1x XYZ-1 and 1x XYZ-2 you have to buy 20 of each (for the gain block case). They've even extended this to high value parts, I use several of their VCOs in a particular product and the VCOs used to be available singly if you so wanted, at a premium obviously. Now VCOs are only sold as a reeled option and you have to buy either 10, 20, 50 or 200 at a time. This is no fun when the VCOs are £40 each in quantity :-(. Currently their minimum order charge is £50 per order.

Conrad, both the parts you mentioned are on their sample scheme, IIRC you can get three samples of each of three products in any thirty day period. You have to fill out a form on line but I’ve never had a problem and they usually get despatched from them to you same day. Obviously things aren't normal at the moment.

It's not quite as good a part but I have a couple of reels of GVA-63+ in stock that you can have a few of if that would help ?

73s Dave


Re: Dishes again - POTY antenna

John E. Beech
 

Hi Graham,
Yes it is very similar. The pattern of ribs on mine is different . From what I can remember the feed arrangement was pretty much the same. I helped install it in the first place, but that was over 20 years ago! Here is what mine actually looks like: https://photos.app.goo.gl/bKwQPhDAVhHXUaxu9
The mount is very heavy - about a half hundred weight or more. It took two of us to lift it onto the car roof rack (behind) but I managed to lift it off on my own. Fortunately, I'm a 17 stone ex-prop forward and although I'm 71 I've retained most of my strength.
The dish is quite light, so I am hoping to use a wall bracket that I've already got off a slightly smaller steel dish. It was originally mounted on a pole set in concrete, but this snapped off at ground level due to corrosion. It was releatively thin wall pipe - less than 1/8". The rest of the mount is made of 1/4 " box section and plate, which is why it is so heavy. And there is the jack and its motor. ( I've got the control box.) Free to a good home.

de John G8SEQ

-------Original Message-------
From: Graham Shirville <graham@shirville.com>
To: UKMicrowaves@groups.io <UKMicrowaves@groups.io>
Subject: Re: [UKMicrowaves] Dishes again - POTY antenna
Sent: May 14 '20 23:17

Sorry - works better with an actual link....it is getting late!

https://forum.batc.org.uk/viewtopic.php?f=101&t=6026

On 14/05/2020 23:10, Graham Shirville wrote:
> Hi John,
>
> Maybe this discussion on the BATC forum last year could help...if it
> is the same sort of dish then somewhere I have also seen a foto with
> the precise lengths of all 3 arms and the LNB bracketry marked up...
>
> 73
>
> Graham G3VZV
>
> On 14/05/2020 21:53, John E. Beech wrote:
>> Hi Paul,
>>              Ah, well I have a bit of a head start. I have 2/3 of the
>> LNB support structure - a long rod and a short rod with information
>> from the previous owner that the short rod went to the bottom of the
>> dish ie the outer edge of the long diameter, so the POTY patch will
>> go somewhere near where  they meet. If I can't get the laser cut bits
>> to hackle I'll knock up a splash plate & crossed dipoles - they've
>> worked on 23 cms in the past with similar focal length dish.
>>
>> de John G8SEQ
>>
>>>   -------Original Message-------
>>>   From: Paul Entwistle via groups.io <g8afc=ntlworld.com@groups.io>
>>>   To: UKMicrowaves@groups.io <UKMicrowaves@groups.io>
>>>   Subject: Re: [UKMicrowaves] Dishes again - POTY antenna
>>>   Sent: May 14 '20 21:08
>>>     John -  It sounds like you have the same dish I have, mine came
>>> without the LNB support structure but I found a DOS based
>>> application written by Paul Wade W1GHZ that worked very well.
>>>   I "think" the link to it came via one of his publications but a
>>> little drilling around "Offset Dish Calculator" should get you there.
>>>     Good Luck
>>>     Paul G8AFC
>>>     -----Original Message-----
>>>   From: UKMicrowaves@groups.io [mailto:UKMicrowaves@groups.io] On
>>> Behalf Of John E. Beech
>>>   Sent: 14 May 2020 19:13
>>>   To: UKMicrowaves@groups.io
>>>   Subject: [UKMicrowaves] Dishes again - POTY antenna
>>>     My latest acquisition is an elliptical ie offset feed dish 1.2 X
>>> 1.35 m which I plan on using on 2.45 GHz Tx for satellite comms.
>>> Question will the POTY patch antenna work with this dish on its own
>>> ie without the 10 GHz LNB. If so how do I mount it? ( 22 mm  Cu tube
>>> up the middle?).
>>>           And (sanity check) the gain of this elliptical dish will
>>> be the same as a prime focus dish of the same (short) diameter.
>>>              Going back to an ealier thread, this dish is all fibre
>>> glass, no metal to be seen anywhere inside or out. ( I know this
>>> because the rim got damaged when it was blown over in a gale.) It
>>> does have a rippled finish a bit like a golf ball which is supposed
>>> to increase the surface area and therefore the gain. That sounds
>>> like bollocks to me - more likely a device for reducing the
>>> reflectivity in the infra red to stop the LNB getting cooked in
>>> bright sunlight.
>>>     de John G8SEQ
>>
>>
>
>
>




Re: Tips for successfully locking Kuhne transverters

Conrad, PA5Y
 

No sooner did I post  I realised that I answered my own question and so I tuned the crystal so it was close to the correct frequency. Then sure enough all was well. I suppose that this thing has been sat in a cupboard at Kuhne for quite some time, the 28MHz IF versions are much less popular. I have RX and TX image response at -90dBc or better (no more dynamic range) and LO leakage is no longer visible. Yes I have a nice filter with notches.

 

Anyway it seems to be very stable now.

 

I had no such problems with the MKU 23 but that was pre-owned and no doubt the previous owner went through this.

 

73

 

Conrad PA5Y

 

From: UKMicrowaves@groups.io <UKMicrowaves@groups.io> On Behalf Of Conrad, PA5Y via groups.io
Sent: 15 May 2020 00:10
To: UKMicrowaves@groups.io
Subject: [UKMicrowaves] Tips for successfully locking Kuhne transverters

 

Hello chaps.

 

Tonight I connected up my Kuhne MKU13 G3 28 for the first time, at the same time I connected my trusty locked TS2000. I tuned to GB3MHZ and as usual it appeared bang on 1296.830 on the locked TS2000. I have a K3S and have no XV Offset. The K3S is locked and with my Iceni on 432 everything is spot on, that injection locks perfectly. The MKU13 locking is quite frankly awful. I have tried 3-10dBm in 1dB steps as an input amplitude. I use the same 10MHz source for everything. I can hear some decidedly strange glitches going on as well. So what is likely to be amiss? I have not connected a lock LED yet. I don’t need one, the frequency offset and glitches tell me that things are not quite right. Do I need to tune the Xtal to get it closer, I suppose that the pull range is somewhat limited?

 

73

 

Conrad


Re: Dishes again - POTY antenna

John E. Beech
 

I did wonder!

-------Original Message-------
From: Graham Shirville <graham@shirville.com>
To: UKMicrowaves@groups.io <UKMicrowaves@groups.io>
Subject: Re: [UKMicrowaves] Dishes again - POTY antenna
Sent: May 14 '20 23:17

Sorry - works better with an actual link....it is getting late!

https://forum.batc.org.uk/viewtopic.php?f=101&t=6026

On 14/05/2020 23:10, Graham Shirville wrote:
> Hi John,
>
> Maybe this discussion on the BATC forum last year could help...if it
> is the same sort of dish then somewhere I have also seen a foto with
> the precise lengths of all 3 arms and the LNB bracketry marked up...
>
> 73
>
> Graham G3VZV
>
> On 14/05/2020 21:53, John E. Beech wrote:
>> Hi Paul,
>>              Ah, well I have a bit of a head start. I have 2/3 of the
>> LNB support structure - a long rod and a short rod with information
>> from the previous owner that the short rod went to the bottom of the
>> dish ie the outer edge of the long diameter, so the POTY patch will
>> go somewhere near where  they meet. If I can't get the laser cut bits
>> to hackle I'll knock up a splash plate & crossed dipoles - they've
>> worked on 23 cms in the past with similar focal length dish.
>>
>> de John G8SEQ
>>
>>>   -------Original Message-------
>>>   From: Paul Entwistle via groups.io <g8afc=ntlworld.com@groups.io>
>>>   To: UKMicrowaves@groups.io <UKMicrowaves@groups.io>
>>>   Subject: Re: [UKMicrowaves] Dishes again - POTY antenna
>>>   Sent: May 14 '20 21:08
>>>     John -  It sounds like you have the same dish I have, mine came
>>> without the LNB support structure but I found a DOS based
>>> application written by Paul Wade W1GHZ that worked very well.
>>>   I "think" the link to it came via one of his publications but a
>>> little drilling around "Offset Dish Calculator" should get you there.
>>>     Good Luck
>>>     Paul G8AFC
>>>     -----Original Message-----
>>>   From: UKMicrowaves@groups.io [mailto:UKMicrowaves@groups.io] On
>>> Behalf Of John E. Beech
>>>   Sent: 14 May 2020 19:13
>>>   To: UKMicrowaves@groups.io
>>>   Subject: [UKMicrowaves] Dishes again - POTY antenna
>>>     My latest acquisition is an elliptical ie offset feed dish 1.2 X
>>> 1.35 m which I plan on using on 2.45 GHz Tx for satellite comms.
>>> Question will the POTY patch antenna work with this dish on its own
>>> ie without the 10 GHz LNB. If so how do I mount it? ( 22 mm  Cu tube
>>> up the middle?).
>>>           And (sanity check) the gain of this elliptical dish will
>>> be the same as a prime focus dish of the same (short) diameter.
>>>              Going back to an ealier thread, this dish is all fibre
>>> glass, no metal to be seen anywhere inside or out. ( I know this
>>> because the rim got damaged when it was blown over in a gale.) It
>>> does have a rippled finish a bit like a golf ball which is supposed
>>> to increase the surface area and therefore the gain. That sounds
>>> like bollocks to me - more likely a device for reducing the
>>> reflectivity in the infra red to stop the LNB getting cooked in
>>> bright sunlight.
>>>     de John G8SEQ
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