Date   

Re: Dean Hill and PepperBox Hill in IO91 - Any experiences?

G4LDR
 

Hello Pete, Trees are the problem on Dean Hill (the weather radar is in a 20m tower so above the trees!). The only good site on Dean Hill is adjacent to the MoD microwave relay tower at IO91EA27MI BUT only if you want to work Hannington to the north east, in other directions trees are a problem. I don't think anyone is planning to go to Hannington. 73 Neil.


Re: mm-wave Contest this Sunday, 20th May

Chris G0FDZ
 

Hi Folks

I will be at Hackpen IO91CL11 with Roger G8CUB and will have 24,47 & 76 GHz, talkback on 144.390 MHz and mobile 07763 109 888.

Regards

Chris G0FDZ


On 18/05/2018 09:42, G3XDY g3xdy@... [ukmicrowaves] wrote:
 

The first of the UK Microwave Group mm-wave contests takes place this
Sunday from 0900-1700z (1000-18000 BST) 0n 24/47/76GHz.

Rules are here: http://microwavers.org/index.htm?contesting.htm

I won't be able to put together an activity list this time, but please
post your plans on the reflector to let others know about your activity.

73

John G3XDY

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mm-wave Contest this Sunday, 20th May

John Quarmby
 

The first of the UK Microwave Group mm-wave contests takes place this Sunday from 0900-1700z (1000-18000 BST) 0n 24/47/76GHz.

Rules are here: http://microwavers.org/index.htm?contesting.htm

I won't be able to put together an activity list this time, but please post your plans on the reflector to let others know about your activity.

73

John G3XDY


Re: Path prediction s/w

Andy G4JNT
 

On 16 May 2018 at 22:44, 'g8zha' g8zha@... [ukmicrowaves] <ukmicrowaves@...> wrote:
 

In a previous employment, I used a path prediction web application made available by the seller of some microwave links. Though it was designed with higher frequencies in mind, I used it to check radio coverage at 180MHz for a PMR scheme. It turned out to be pretty accurate.

 

It has been a few years now since I was in the radio business and I cannot remember where the web app was.

 

Can anyone point me towards some software to look at path profiles and coverage areas?

 

Rgds Rich



Re: Dean Hill and PepperBox Hill in IO91 - Any experiences?

John McCarthy
 

Forget pepper Box Hill too many trees, don't know about Dean hill. But your right the first two are good sites.

All best John G7JTT




On Thu, 17 May 2018 at 23:18, Peter Walsh peterdwberkshire@... [ukmicrowaves]
wrote:
 


Hi Microwavers,

Just wondering to go for 24G and 10G UKuG contests over the next 2 Sundays. 

Fancy roving in IO91, between 4 sites and I'm looking at Lane End, Cheesefoot Head near Winchester and also taking in PepperBox Hill and Dean Hill.  To plan I've using the very handy BATC Google overlay of UK ATV and Microwave sites here: https://bit.ly/2ImUTVA

The first of these two sites Lane End and Cheesefoot Head look excellent and I've worked people who have been in those locations before.  The PepperBox Hill and Dean Hill locations I've not been to does anyone have any experience of operating from those? Access? Hedges? Good path directions? 

Looks like Dean Hill has a Met Office Radar installation on it: https://www.metoffice.gov.uk/news/releases/2017/new-state-of-the-art-radar-for-dean-hill so wont get too close to that!

Any thoughts on these sites (or any others in IO91) welcomed. 
Hope to work a few of you on 24G and 10G soon. 

Regards..Pete
G1DFL
07713 432632





Path prediction s/w

g8zha <g8zha@...>
 

In a previous employment, I used a path prediction web application made available by the seller of some microwave links. Though it was designed with higher frequencies in mind, I used it to check radio coverage at 180MHz for a PMR scheme. It turned out to be pretty accurate.

 

It has been a few years now since I was in the radio business and I cannot remember where the web app was.

 

Can anyone point me towards some software to look at path profiles and coverage areas?

 

Rgds Rich


9cm transverter

mike G6TRM
 

Hi,
 Can anyone help? I am looking for a DB6NT Khune Electronics transverter for 9cm. pref 2M or 70cm IF
Anything considered, new,old, kit etc

thanks

Mike G6TRM



Dean Hill and PepperBox Hill in IO91 - Any experiences?

G1DFL
 


Hi Microwavers,

Just wondering to go for 24G and 10G UKuG contests over the next 2 Sundays. 

Fancy roving in IO91, between 4 sites and I'm looking at Lane End, Cheesefoot Head near Winchester and also taking in PepperBox Hill and Dean Hill.  To plan I've using the very handy BATC Google overlay of UK ATV and Microwave sites here: https://bit.ly/2ImUTVA

The first of these two sites Lane End and Cheesefoot Head look excellent and I've worked people who have been in those locations before.  The PepperBox Hill and Dean Hill locations I've not been to does anyone have any experience of operating from those? Access? Hedges? Good path directions? 

Looks like Dean Hill has a Met Office Radar installation on it: https://www.metoffice.gov.uk/news/releases/2017/new-state-of-the-art-radar-for-dean-hill so wont get too close to that!

Any thoughts on these sites (or any others in IO91) welcomed. 
Hope to work a few of you on 24G and 10G soon. 

Regards..Pete
G1DFL
07713 432632





Re: Article on antenna direction sensor?

Eric Schumacher <wb6kcn@...>
 

If you browse the   radioartisan   archives there is much info on using compass modules for antenna pointing.  https://groups.io/g/radioartisan      Sample below:

WB6KCN

 

From: radioartisan@groups.io [mailto:radioartisan@groups.io] On Behalf Of Rick VK6RK
Sent: Monday, May 14, 2018 10:57 PM
To: radioartisan@groups.io
Subject: Re: [radioartisan] #arduinorotatorcontroller

 

Hi Boris.

That's interesting.

Here's my experience with them

There was another project I was experimenting with and I thought I had a real HMC.  I could not get it to work.  Then I found out it was actually a QMC.  I too tried many libraries without success until I stumbled upon the DFROBOT.  Worked well.
I even bought a true HMC, swapped it into the project and the with the DFROBOT library, the HMC was sensed and it worked fine.  I could interchange between both compasses with hardware only, not touching any software.

The difference between the 2 is a different address and a few of the registers have changed.

HMC on the left, QMC on the right.  All the QMC's I've seen, have 'DA' on the chip whereas the HMC's don't.



73,
Rick VK6RK

 

On 15/05/2018 13:28, Boris T. wrote:

Hi Rick, yes, I tried all library's in code, include DFROBOT... but DFROBOT doesn't work with my HMC5883L GY-271. Somewhere on net, I found some topics that these GY-271 is not real HMC, in fact it's QMC. If I understand well, there are too many varietis of similar chip and you need kilometric code (if you want include library's) for all these kind of sensors (GY271, GY273 etc).
73, Boris YU7MW

 

 

 

From: ukmicrowaves@... [mailto:ukmicrowaves@...]
Sent: Sunday, May 13, 2018 3:02 AM
To: ukmicrowaves@...
Subject: Re: [ukmicrowaves] Article on antenna direction sensor?

 

 

Andy,

I found in the hardcopy Radcom and the Electronic Compass Module article. I like your two-wire interface with optional polarity.

I have used PICs in the past, but I may go posh and try Arduinos.

I found Design Notes articles up to July 2017 on the RSGB site.

73 Graham - G3YJR


Re: Hatfield 2700 series relays

Martin A Hall <gorrell77@...>
 

Hi Alan,

Fantastic!  Many thanks for the data sheet, just what I wanted; received OK at my Tiscali address  Your efforts to dig out and scan the information are much appreciated.  It’s a higher spec than I’d anticipated, which is good news, and easily meets my requirements.

Very best wishes,

Martin

GM8IEM

 

From: ukmicrowaves@...
Sent: 14 May 2018 11:09
To: ukmicrowaves@...
Subject: [ukmicrowaves] Hatfield 2700 series relays

 

 

Hi Martin I have found the sheet for the 2700 series relays I will scan it
and forward to your tiscali address?? I was mistaken they are spec'd up to
1000MHz

Alan
G3NYK


432 and Above EME Newsletter for June 2018

rein0zn@...
 

Hello All,

The 432 MHz and Above EME Newsletter for June 2018 by K2UYH can be downloaded from:

http://www.nitehawk.com/rasmit/em70cm.html

-- Enjoy

-- Tnx Al.


73 Rein W6SZ


Surplus microwave kit

Chris G8BKE
 


Roy G3FYX has the following equipment surplus to requirements:-
 
 
Marconi TFT Power Meter System Type 6460/1, 10MHz to 18GHz with coax and
Waveguide heads, cable,  handbook and 20dB attentuator.
 
------------------------------------------------------------------------------------------------------------------------
 
Also  TWO Telonic - Barclay rotary stepped attenuators fitted with SMA connectors.
 
One is 0 -10dB in 1 dB steps; the other 0 -100dB in 10dB steps. They are mounted in a box as
a pair with N type connectors.
 
------------------------------------------------------------------------------------------------------------------------
 
An ICOM 2m IC202E in good condition
 
plus
 
a second ICOM 2m  IC202 with low power output but with a low noise front end. Ideal for driving
transverters
 
 
 
Items would be available for collection at RAL to interested parties 
 
 
Anyone interested should contact Roy OFF the reflector on e mail:  g3fyx (at) tiscali.co.uk for
more information.


73 de Chris G8BKE
 
Website:  www.g8bke.co.uk



Re: Article on antenna direction sensor?

hmyjr@...
 

Thanks for the tip about the microbit Stuart.

Graham G3YJR


Re: Article on antenna direction sensor?

Stuart G1ZAR
 

Quite a few articles / projects on using an Arduino as a magnetic compass.
My own thoughts were to use a BBC microbit, as it has the compass module built in.

73 Stuart
G1ZAR


Re: Advice

KENT BRITAIN
 

No, just mount the Vivaldi out there.

OK for portable use, for home use some kind of weather protection is suggested.



From: "'g7jtt@...' g7jtt@... [ukmicrowaves]" <ukmicrowaves@...>
To: "ukmicrowaves@..." ; "ukmicrowaves@..."
Sent: Monday, May 14, 2018 6:44 AM
Subject: Re: [ukmicrowaves] Re: Advice

 
Just thinking ahead does the Vivaldi need a back plate when being used to feed a dish?  And if so should it be soldered to the back edge of the pcb?  

Cheers John


On Mon, 14 May 2018 at 6:52, 'g7jtt@...' g7jtt@... [ukmicrowaves]
<ukmicrowaves@...> wrote:
 
Thanks Ole that's reassuring to know that with a small mod it's possible to run at high power. 

John


On Sun, 13 May 2018 at 22:14, 'Ole Nykjær' ole@... [ukmicrowaves]
wrote:
 
[Attachment(s) from Ole =?utf-8?Q?Nykj=C3=A6r?= included below]
 Hi all - I have been using one of Kent's Log Periodic antennas as feed for a 13+9 cm dish for some years now. As I run power on both bands (240W on 13cm and 80W on 9 cm, unfortunately only half at the feed) burnout of the PCB elements was a concern. I modified the antenna - a 2.1-5 GHz design - by soldering thicker wires on top of all the PCB tracks. This reduces the ohmic losses in the elements and the central feed structure (and improves cooling). To keep with the idea of the logarithmic antenna, I have used different diameter wires. See picture.

Adding the wires had the effect of raising the low frequency limit, so matching on 13 cm was compromised. I extended the rear 2 elements on each side by abt. 10 mm, until I had a reasonable return loss. This was done after the photo had been taken...

73 Ole OZ2OE

Den 13. maj 2018 kl. 19.00.21 +02.00, skrev 'jewell@...' jewell@... [ukmicrowaves] :
 
Now dealing with it....

Sam




On Sunday, May 13, 2018, 5:37 pm, KENT BRITAIN WA5VJB@... [ukmicrowaves] wrote:
 

Since I gave Sam an handful just a few weeks ago, he should have the 1.5-15's.
And at reduced performance they do work down to 800 MHz.

Wish I had enough power to test them to destruction.
50 watts of SSB or CW should be fine.   FM or one of the near CW digital modes
would be close, sort of depends on the length of your feedline.

BUT, it you cook it, let me know at what power level, and I will get you another one.
Good data point.



From: "'g7jtt@...' g7jtt@... [ukmicrowaves]"
To: "uk microwaves@..."
Sent: Sunday, May 13, 2018 11:22 AM
Subject: Re: [ukmicrowaves] Re: Advice

 
Hi Kent thanks for a very informative reply I have one of your log periodic pcb antenna's so will give that a try. I see G4DDK does not stock your 1.5 to 15Ghz Vivaldi antenna, is there any likely hood of this changing ? If not will need to order directly . Also what is the power handling of the antenna's as I have around 50w on 23cm and 13cm whilst only 2w on 3cm.

All best John



On Sun, 13 May 2018 at 15:44, KENT BRITAIN WA5VJB@... [ukmicrowaves]
wrote:
 

Log Periodics do work well as a dish feed.
I agree, not quite as well as an optimized scalar feed, but the difference
is about 1 dB on a small dish.  And you get 3 or 4 ham bands.

The feedpoint of a dish is a theoretical point and usually calculated as though the
dish is used at optical frequencies.    In testing well over 100 dishes, the optimal
position for the feed is almost always closer to the dish than the calculated feed point.
In part this is because the feed is not an infinitesimal point.

Yes, the phase center of a log periodic does move, but it doesn't move very much.
When optimized at the highest frequency of use, the phase error at the lowest
frequency of use is quite minor.

Another option is using a Vivaldi antenna for the feed. nbsp; I like to think of a Vivaldi
and a Ridged Horn without the horn.    Phase center is pretty constant with
frequency.   The Vivaldi has about 2 dB more gain than a Log Periodic and would
be more suitable for most offset fed dishes.

73  G8EMY/W5



From: "g7jtt@... [ukmicrowaves]" <ukmicrowaves@...>
To: ukmicrowaves@yahoogroups...com
Sent: Sunday, May 13, 2018 7:44 AM
Subject:< /span> [ukmicrowaves] Re: Advice

 
just came across this site which has a multi band ring feed http://gvnweb.ddns.net:8081/dish1.html and links to some design software as well. the only thing is this is used on a prime focus dish are these feeds ok to use with an off set dish ?

cheers John 

















Re: Advice

John McCarthy
 

Just thinking ahead does the Vivaldi need a back plate when being used to feed a dish?  And if so should it be soldered to the back edge of the pcb?  

Cheers John


On Mon, 14 May 2018 at 6:52, 'g7jtt@...' g7jtt@... [ukmicrowaves]
wrote:
 

Thanks Ole that's reassuring to know that with a small mod it's possible to run at high power. 


John


On Sun, 13 May 2018 at 22:14, 'Ole Nykjær' ole@... [ukmicrowaves]
wrote:
 
[Attachment(s) from Ole =?utf-8?Q?Nykj=C3=A6r?= included below]

 Hi all - I have been using one of Kent's Log Periodic antennas as feed for a 13+9 cm dish for some years now. As I run power on both bands (240W on 13cm and 80W on 9 cm, unfortunately only half at the feed) burnout of the PCB elements was a concern. I modified the antenna - a 2.1-5 GHz design - by soldering thicker wires on top of all the PCB tracks. This reduces the ohmic losses in the elements and the central feed structure (and improves cooling). To keep with the idea of the logarithmic antenna, I have used different diameter wires. See picture.

Adding the wires had the effect of raising the low frequency limit, so matching on 13 cm was compromised. I extended the rear 2 elements on each side by abt. 10 mm, until I had a reasonable return loss. This was done after the photo had been taken..

73 Ole OZ2OE

Den 13. maj 2018 kl. 19.00.21 +02.00, skrev 'jewell@...' jewell@... [ukmicrowaves] :
 

Now dealing with it....


Sam




On Sunday, May 13, 2018, 5:37 pm, KENT BRITAIN WA5VJB@... [ukmicrowaves] wrote:

 


Since I gave Sam an handful just a few weeks ago, he should have the 1.5-15's.
And at reduced performance they do work down to 800 MHz.

Wish I had enough power to test them to destruction.
50 watts of SSB or CW should be fine.   FM or one of the near CW digital modes
would be close, sort of depends on the length of your feedline.

BUT, it you cook it, let me know at what power level, and I will get you another one.
Good data point.



From: "'g7jtt@...' g7jtt@... [ukmicrowaves]"
To: "uk microwaves@..."
Sent: Sunday, May 13, 2018 11:22 AM
Subject: Re: [ukmicrowaves] Re: Advice

 
Hi Kent thanks for a very informative reply I have one of your log periodic pcb antenna's so will give that a try. I see G4DDK does not stock your 1.5 to 15Ghz Vivaldi antenna, is there any likely hood of this changing ? If not will need to order directly . Also what is the power handling of the antenna's as I have around 50w on 23cm and 13cm whilst only 2w on 3cm.

All best John



On Sun, 13 May 2018 at 15:44, KENT BRITAIN WA5VJB@... [ukmicrowaves]
 

Log Periodics do work well as a dish feed.
I agree, not quite as well as an optimized scalar feed, but the difference
is about 1 dB on a small dish.  And you get 3 or 4 ham bands.

The feedpoint of a dish is a theoretical point and usually calculated as though the
dish is used at optical frequencies.    In testing well over 100 dishes, the optimal
position for the feed is almost always closer to the dish than the calculated feed point.
In part this is because the feed is not an infinitesimal point.

Yes, the phase center of a log periodic does move, but it doesn't move very much.
When optimized at the highest frequency of use, the phase error at the lowest
frequency of use is quite minor.

Another option is using a Vivaldi antenna for the feed. nbsp; I like to think of a Vivaldi
and a Ridged Horn without the horn.    Phase center is pretty constant with
frequency.   The Vivaldi has about 2 dB more gain than a Log Periodic and would
be more suitable for most offset fed dishes.

73  G8EMY/W5



From: "g7jtt@... [ukmicrowaves]"
To: ukmicrowaves@yahoogroups..com
Sent: Sunday, May 13, 2018 7:44 AM
Subject:< /span> [ukmicrowaves] Re: Advice

 
just came across this site which has a multi band ring feed http://gvnweb.ddns.net:8081/dish1.html and links to some design software as well. the only thing is this is used on a prime focus dish are these feeds ok to use with an off set dish ?

cheers John 















Hatfield 2700 series relays

Alan Melia
 

Hi Martin I have found the sheet for the 2700 series relays I will scan it and forward to your tiscali address?? I was mistaken they are spec'd up to 1000MHz

Alan
G3NYK


re Hatfield Insts relay

Alan Melia
 

Hi Martin, I recollect seeing something like that in my ''collection'' :-)) From memory its rated to about 200MHz, I am sure I have a data sheet for that series, but it may take a little time to find :-)) I will get back if I can locate the paperwork.

Alan
G3NYK


Re: Advice [1 Attachment]

John McCarthy
 

Thanks Ole that's reassuring to know that with a small mod it's possible to run at high power. 

John


On Sun, 13 May 2018 at 22:14, 'Ole Nykjær' ole@... [ukmicrowaves]
wrote:
 
[Attachment(s) from Ole =?utf-8?Q?Nykj=C3=A6r?= included below]

 Hi all - I have been using one of Kent's Log Periodic antennas as feed for a 13+9 cm dish for some years now. As I run power on both bands (240W on 13cm and 80W on 9 cm, unfortunately only half at the feed) burnout of the PCB elements was a concern. I modified the antenna - a 2.1-5 GHz design - by soldering thicker wires on top of all the PCB tracks. This reduces the ohmic losses in the elements and the central feed structure (and improves cooling). To keep with the idea of the logarithmic antenna, I have used different diameter wires. See picture.

Adding the wires had the effect of raising the low frequency limit, so matching on 13 cm was compromised. I extended the rear 2 elements on each side by abt. 10 mm, until I had a reasonable return loss. This was done after the photo had been taken.

73 Ole OZ2OE

Den 13. maj 2018 kl. 19.00.21 +02.00, skrev 'jewell@...' jewell@... [ukmicrowaves] :
 

Now dealing with it....


Sam




On Sunday, May 13, 2018, 5:37 pm, KENT BRITAIN WA5VJB@... [ukmicrowaves] wrote:

 


Since I gave Sam an handful just a few weeks ago, he should have the 1.5-15's.
And at reduced performance they do work down to 800 MHz.

Wish I had enough power to test them to destruction.
50 watts of SSB or CW should be fine.   FM or one of the near CW digital modes
would be close, sort of depends on the length of your feedline.

BUT, it you cook it, let me know at what power level, and I will get you another one.
Good data point.



From: "'g7jtt@...' g7jtt@... [ukmicrowaves]"
To: "uk microwaves@..." <ukmicrowaves@...>
Sent: Sunday, May 13, 2018 11:22 AM
Subject: Re: [ukmicrowaves] Re: Advice

 
Hi Kent thanks for a very informative reply I have one of your log periodic pcb antenna's so will give that a try. I see G4DDK does not stock your 1.5 to 15Ghz Vivaldi antenna, is there any likely hood of this changing ? If not will need to order directly . Also what is the power handling of the antenna's as I have around 50w on 23cm and 13cm whilst only 2w on 3cm.

All best John



On Sun, 13 May 2018 at 15:44, KENT BRITAIN WA5VJB@... [ukmicrowaves]
wrote:
 

Log Periodics do work well as a dish feed.
I agree, not quite as well as an optimized scalar feed, but the difference
is about 1 dB on a small dish.  And you get 3 or 4 ham bands.

The feedpoint of a dish is a theoretical point and usually calculated as though the
dish is used at optical frequencies.    In testing well over 100 dishes, the optimal
position for the feed is almost always closer to the dish than the calculated feed point.
In part this is because the feed is not an infinitesimal point.

Yes, the phase center of a log periodic does move, but it doesn't move very much.
When optimized at the highest frequency of use, the phase error at the lowest
frequency of use is quite minor.

Another option is using a Vivaldi antenna for the feed. nbsp; I like to think of a Vivaldi
and a Ridged Horn without the horn.    Phase center is pretty constant with
frequency.   The Vivaldi has about 2 dB more gain than a Log Periodic and would
be more suitable for most offset fed dishes.

73  G8EMY/W5



From: "g7jtt@... [ukmicrowaves]"
To: ukmicrowaves@...
Sent: Sunday, May 13, 2018 7:44 AM
Subject:< /span> [ukmicrowaves] Re: Advice

 
just came across this site which has a multi band ring feed http://gvnweb.ddns.net:8081/dish1.html and links to some design software as well. the only thing is this is used on a prime focus dish are these feeds ok to use with an off set dish ?

cheers John 















Re: Advice

Ole OZ2OE
 

 Hi all - I have been using one of Kent's Log Periodic antennas as feed for a 13+9 cm dish for some years now. As I run power on both bands (240W on 13cm and 80W on 9 cm, unfortunately only half at the feed) burnout of the PCB elements was a concern. I modified the antenna - a 2.1-5 GHz design - by soldering thicker wires on top of all the PCB tracks. This reduces the ohmic losses in the elements and the central feed structure (and improves cooling). To keep with the idea of the logarithmic antenna, I have used different diameter wires. See picture.

Adding the wires had the effect of raising the low frequency limit, so matching on 13 cm was compromised. I extended the rear 2 elements on each side by abt. 10 mm, until I had a reasonable return loss. This was done after the photo had been taken.

73 Ole OZ2OE

Den 13. maj 2018 kl. 19.00.21 +02.00, skrev 'jewell@...' jewell@... [ukmicrowaves] :

 

Now dealing with it....


Sam




On Sunday, May 13, 2018, 5:37 pm, KENT BRITAIN WA5VJB@... [ukmicrowaves] wrote:

 


Since I gave Sam an handful just a few weeks ago, he should have the 1.5-15's.
And at reduced performance they do work down to 800 MHz.

Wish I had enough power to test them to destruction.
50 watts of SSB or CW should be fine.   FM or one of the near CW digital modes
would be close, sort of depends on the length of your feedline.

BUT, it you cook it, let me know at what power level, and I will get you another one.
Good data point.



From: "'g7jtt@...' g7jtt@... [ukmicrowaves]"
To: "uk microwaves@..."
Sent: Sunday, May 13, 2018 11:22 AM
Subject: Re: [ukmicrowaves] Re: Advice

 
Hi Kent thanks for a very informative reply I have one of your log periodic pcb antenna's so will give that a try. I see G4DDK does not stock your 1.5 to 15Ghz Vivaldi antenna, is there any likely hood of this changing ? If not will need to order directly . Also what is the power handling of the antenna's as I have around 50w on 23cm and 13cm whilst only 2w on 3cm.

All best John



On Sun, 13 May 2018 at 15:44, KENT BRITAIN WA5VJB@... [ukmicrowaves]
wrote:
 

Log Periodics do work well as a dish feed.
I agree, not quite as well as an optimized scalar feed, but the difference
is about 1 dB on a small dish.  And you get 3 or 4 ham bands.

The feedpoint of a dish is a theoretical point and usually calculated as though the
dish is used at optical frequencies.    In testing well over 100 dishes, the optimal
position for the feed is almost always closer to the dish than the calculated feed point.
In part this is because the feed is not an infinitesimal point.

Yes, the phase center of a log periodic does move, but it doesn't move very much.
When optimized at the highest frequency of use, the phase error at the lowest
frequency of use is quite minor.

Another option is using a Vivaldi antenna for the feed.& nbsp; I like to think of a Vivaldi
and a Ridged Horn without the horn.    Phase center is pretty constant with
frequency.   The Vivaldi has about 2 dB more gain than a Log Periodic and would
be more suitable for most offset fed dishes.

73  G8EMY/W5



From: "g7jtt@... [ukmicrowaves]"
To: ukmicrowaves@...
Sent: Sunday, May 13, 2018 7:44 AM
Subject:< /span> [ukmicrowaves] Re: Advice

 
just came across this site which has a multi band ring feed http://gvnweb.ddns.net:8081/dish1.html and links to some design software as well. the only thing is this is used on a prime focus dish are these feeds ok to use with an off set dish ?

cheers John 














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