Date   

Retuning a 23cm duplexer, any hints please?

Alan Beard
 

Hi all,

I've just attempted to retune this duplexer from Radio Frequency Systems P/L.
Model: CP1800-I42

Originally on 1710 and 1910 MHz. It tuned down to 1273 and 1293 MHz OK but
kept the same "channel" bandwidth of about 20 MHz. (the width of the pass band)

So, it's skirts only attenuate 45db or so the Tx carrier and/or the
Tx spurii.

I note the inter digital coupling screws do nothing and I mean nothing
to reduce the coupling and thus the filter bandwidth. (the three on the
left and right ends of the top cover)

Has anyone any thoughts on making it useful for our 20MHz split 23cm
repeaters?


---------------------------------------------------
Alan VK2ZIW
Before the Big Bang, God, Sela.
OpenWebMail 2.53, nothing in the cloud.


Portable Operation in UKuG Contests

John Quarmby
 

The next UK Microwave Group contest is the LowBand event on 11th April from 10:00 - 16:00 GMT (11:00 - 17:00 BST) on the 1296, 2300, 2320, and 3400MHz bands.

As some of the lock down rules have been relaxed, portable entries will now be accepted.

73

John G3XDY
UKuG Contest Manager


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Re: Where is the focal point of an LNB?

Chris Wilson
 

Hello Mike,

Thursday, April 1, 2021

Thanks Mike and to all who replied, making it adjustable seems the easiest and most practical way, so that's what I will do :)


Best regards,
Chris 2E0ILY mailto:chris@chriswilson.tv


MW> PS - 6 photos of the feed but not one of the actual dish? Given
MW> it is a tripod feed I would suggest you make the mount adjustable.
MW> Then you can optimise it in situ.


Re: Where is the focal point of an LNB?

Chris Wilson
 

Hello Neil,

Thursday, April 1, 2021

This is what I was afraid of Neil. The set up worked fine, but terrestrial satellites and a 1.8 meter dish gives a lot of leeway, so I will see how I can give things some adjustability, thank you.

Best regards,
Chris 2E0ILY mailto:chris@chriswilson.tv


NSG> With unknown dishes, I don't trust the current location of the
NSG> feedpoint, I make a temporary bracket which can slide along the
NSG> LNB axis and use sun noise to find the optimal position, verify
NSG> using a longish optical path, then measure the position and make
NSG> a permanent clamp with a couple of cm adjustment.

NSG> Neil G4DBN
NSG>
NSG>
NSG>
NSG>


Re: Where is the focal point of an LNB?

Neil Smith G4DBN
 

Hi Keith, it's a Pickett-Potter I made to the WA6KBL design for 3cm, linear dual-mode, fed with WR90 through a tuned oval iris

Neil

On 02/04/2021 14:14, Keith wrote:
Neil,
Is that feed one of the RF Hamdesign horn feeds ?
I was originally looking at that design for 8.45 ghz, but have since gone to a squeezed tube polariser.
Cheers
Keith
VK6KB / VK6EME


Re: Where is the focal point of an LNB?

Keith
 

Neil, 
Is that feed one of the RF Hamdesign horn feeds ?
I was originally looking at that design for 8.45 ghz, but have since gone to a squeezed tube polariser.
Cheers
Keith 
VK6KB / VK6EME


Re: Looking for data on 23cm G3JVL 47-ele loop yagi.

andrew marshall
 

Hi Andy,

Thank you for your reply. That's saved me having to d/l it.

73,
Andrew.


Re: Looking for data on 23cm G3JVL 47-ele loop yagi.

andrew marshall
 

Hi John,

Thank you for your reply. I'll do a search for that company and see whether there's a close-enough antenna to the 'JVL 47-ele.

73,
Andrew.


Re: Looking for data on 23cm G3JVL 47-ele loop yagi.

andrew marshall
 

Hi Kent,

Thank you for your reply. I'll use 20dBi as input to the RSGB calculator and see if I'm compliant with 10W RF into 8m of H100.

73,
Andrew.


Re: Looking for data on 23cm G3JVL 47-ele loop yagi.

John Lemay
 

Andrew

 

Directive Systems in the USA sell a range of loop yagis and their specification includes gain. You will probably find one of a comparable size to yours.

 

John G4ZTR

 

From: UKMicrowaves@groups.io [mailto:UKMicrowaves@groups.io] On Behalf Of andrew marshall
Sent: 01 April 2021 17:55
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Looking for data on 23cm G3JVL 47-ele loop yagi.

 

Hi Stuart,

Thanks for your reply.

I'll do a search for the loop quad calc program and see whether there's a way forward there. For security reasons my Net-connected machines run Linux so if the program needs Windows that might be a problem - we'll see.

73,

Andrew, G8BUR, M0MAA.


Re: Looking for data on 23cm G3JVL 47-ele loop yagi.

KENT BRITAIN
 

20 dBi gain is typical   15 deg 3 dB beamwidth is typical

Plus or Minus a few seasons of weathering.

Kent


On Thursday, April 1, 2021, 11:54:39 AM CDT, andrew marshall <g8bur@...> wrote:


Hi Stuart,

Thanks for your reply.

I'll do a search for the loop quad calc program and see whether there's a way forward there. For security reasons my Net-connected machines run Linux so if the program needs Windows that might be a problem - we'll see.

73,
Andrew, G8BUR, M0MAA.


Re: Looking for data on 23cm G3JVL 47-ele loop yagi.

Andy G4JNT
 

My copy of LOOPQUAD (old 16 bit DOS, had to be run in an emulator) doesn't give antenna gain.



On Thu, 1 Apr 2021 at 17:54, andrew marshall <g8bur@...> wrote:
Hi Stuart,

Thanks for your reply.

I'll do a search for the loop quad calc program and see whether there's a way forward there. For security reasons my Net-connected machines run Linux so if the program needs Windows that might be a problem - we'll see.

73,
Andrew, G8BUR, M0MAA.


Re: Looking for data on 23cm G3JVL 47-ele loop yagi.

andrew marshall
 

Hi Stuart,

Thanks for your reply.

I'll do a search for the loop quad calc program and see whether there's a way forward there. For security reasons my Net-connected machines run Linux so if the program needs Windows that might be a problem - we'll see.

73,
Andrew, G8BUR, M0MAA.


Re: Looking for data on 23cm G3JVL 47-ele loop yagi.

Stuart G1ZAR
 

Andrew, does it give you that information in the JVL Loop Quad calculation program?

regards...........Stuart


Looking for data on 23cm G3JVL 47-ele loop yagi.

andrew marshall
 

As part of my plans to raise my EMF compliance documentation, I am looking for gain and beamwidth/polar diagram data for my G3JVL 23cm 47-element loop Yagi. I have no paperwork for it here, and I have so far been unable to find any data via web search. I'd very much appreciate this data if anyone has it to hand or can point me at a link.

TIA.

73,
Andrew, G8BUR, M0MAA.


Re: Hempt? ... OT: wanted H1681 or HWF 1681 RA (HexaWave) Rf final

green
 


hi,

I am trying to find some power Rf Mesfets (?) in ceramic white packages labeled :    H 1681   or   HWF1681RA  ,  made by HexaWave (?)
I need some to repair a 6 GHz Signal Generator, ( Aeroflex 3416 )
 
I have the data sheet, but can't seem to find a suitable device.

thank you,
rick


Re: Where is the focal point of an LNB?

G0FVI
 

Chris, I also use a 1.8m TVRO dish for Es'Hail. I'd agree with what has been said that the focal point is not usually where cacluated. My POTY fits nicely inside a purchased LNB holder using two 22mm plumbing nuts that fit around the body of the POTY, enclosed by the cut off neck from the modified LNB. This 'minimum' engineering solution allows moving focal point in or out a fair bit to achieve maximum signal from Es'Hail (see pic). The focal point for 2.4GHz uplink is not the same as 10GHz downlink but with a dish this size for Es'Hail you really don't have to worry too much (you'll be S9+ in and be getting a decent downlink signal). With your dish you'll just need to modify the cental strut ring to allow a POTY to fit in there.


  


Re: Where is the focal point of an LNB?

KENT BRITAIN
 

Neil, I 101% agree with you.  I have NEVER found to focus to be at the calculated point!
The vast majority of the time gain improves when the feed is a bit closer to the dish.
Test if you can!   Kent G8EMY/W5

On Thursday, April 1, 2021, 8:25:54 AM CDT, Neil Smith G4DBN <neil@...> wrote:


With unknown dishes, I don't trust the current location of the feedpoint, I make a temporary bracket which can slide along the LNB axis and use sun noise to find the optimal position, verify using a longish optical path, then measure the position and make a permanent clamp with a couple of cm adjustment.

Neil G4DBN



Re: Where is the focal point of an LNB?

Neil Smith G4DBN
 

With unknown dishes, I don't trust the current location of the feedpoint, I make a temporary bracket which can slide along the LNB axis and use sun noise to find the optimal position, verify using a longish optical path, then measure the position and make a permanent clamp with a couple of cm adjustment.

Neil G4DBN



Re: Where is the focal point of an LNB?

Mike Willis
 

PS - 6 photos of the feed but not one of the actual dish? Given it is a tripod feed I would suggest you make the mount adjustable. Then you can optimise it in situ.
--
Mike G0MJW

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