Date   
Re: mind gone blank - guide wavelength in terms of radius?

Neil Smith G4DBN
 

Thanks Dave. Weirdly on my Mac, I can’t resolve the scan, it is all blurry. I’ll have a look on a windows or Android in the morning, unless you can make the image a bit bigger?
Ta, Neil

On 12 Jul 2019, at 00:44, Dave Brown <2c39a@...> wrote:

This might help- had Vol 5 handy as was looking something up the other day.
73
Dave, ZL3FJ

-----Original Message-----
From: UKMicrowaves@groups.io [mailto:UKMicrowaves@groups.io] On Behalf Of Neil Smith G4DBN
Sent: Friday, July 12, 2019 11:00
To: UKMicrowaves@groups.io
Subject: [UKMicrowaves] mind gone blank - guide wavelength in terms of radius?

Having one of those moments. For TE01 in a circular guide, the cutoff is 1.8412c/(2*pi*r), but what is the correct expression for guide wavelength? I sort-of think it is the same as for rectangular in terms of cutoff, but now I am riddled with self-doubt. Awful long time since Bill Duffin taught me this stuff when I was a callow youth.

Neil G4DBN







<ScanImage002.jpg>

Re: mind gone blank - guide wavelength in terms of radius?

Dave Brown
 

This might help- had Vol 5 handy as was looking something up the other day.
73
Dave, ZL3FJ

-----Original Message-----
From: UKMicrowaves@groups.io [mailto:UKMicrowaves@groups.io] On Behalf Of Neil Smith G4DBN
Sent: Friday, July 12, 2019 11:00
To: UKMicrowaves@groups.io
Subject: [UKMicrowaves] mind gone blank - guide wavelength in terms of radius?

Having one of those moments. For TE01 in a circular guide, the cutoff is 1.8412c/(2*pi*r), but what is the correct expression for guide wavelength? I sort-of think it is the same as for rectangular in terms of cutoff, but now I am riddled with self-doubt. Awful long time since Bill Duffin taught me this stuff when I was a callow youth.

Neil G4DBN

Re: PE1RKI 23 Cm Low loss filter responce

simonchettle
 

Pete

After a fair bit of re-build of the station (pre nfd) we became a bit of an a alligator based on the reports we were receiving and were giving. so a rebuild of the station is being considered. the use of 28 Mhz IF is to avoid the 2M and 70 Cm contest stations as they run a lot of power.s Also the 23 cm pre-amp measured 1.5 db nf (including relays and connectors) when tested but something may have failed on trip to site -tests to performed this week end.

73s and thanks for the replies

simon

-----Original Message-----
From: Pete - GM4BYF via Groups.Io
Sent: Thursday, July 11, 2019 7:51 PM
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] PE1RKI 23 Cm Low loss filter responce

From Phils picture, I think Bert did understand your question.
Guestimating from the grid there appears to be very little roll off
between 1268 and 1296.

I wonder what your problems were on field day ? Transmit or receive or both?

73
Pete GM4BYF

On 11/07/19 19:12, Phil Guttridge G3TCU wrote:
Hi Simon,

I bought a 23cm filter from Bert earlier this year and he sent me this
link. It doesn't show a lot of detail on the spectrum axis but it might
be some guide.

https://www.flickr.com/photos/pe1rki/23099962502/in/album-72157658763409636/

73, Phil G3TCU

On 11/07/2019 18:33, simonchettle via Groups.Io wrote:
Hi All
I am thinking of using a 28 Mhz to 1296 transverter as part of a
Station re-build ( after poor result on VHD NFD!).
However I do not know the passband rejection of the above filter at
1268 Mhz. I have mailed Bert and he has replied the loss / rejection
is 0.99 dB – I think he slightly misunderstood my question to him.
Has anybody measured the rejection at 1268 of one of his filters? His
current web site does not appear to display the filter response and I
am sure it used to.
Cheers
Simon G8ATB

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--
vry 73
Pete GM4BYF

mind gone blank - guide wavelength in terms of radius?

Neil Smith G4DBN
 

Having one of those moments. For TE01 in a circular guide, the cutoff is 1.8412c/(2*pi*r), but what is the correct expression for guide wavelength?  I sort-of think it is the same as for rectangular in terms of cutoff, but now I am riddled with self-doubt. Awful long time since Bill Duffin taught me this stuff when I was a callow youth.

Neil G4DBN

Re: Help with SMA leads

Neil Smith G4DBN
 

Ah, I see. SMA might not be the best choice for that, depending on the number of connect-disconnect cycles.  Most SMAs have very limited numbers of permitted cycles. Is TNC an option?

Neil


On 11/07/2019 22:39, G8TZJ via Groups.Io wrote:
Thanks for the suggestions. I will look at these web sites and see who can provide the most suitable leads. In reply to G4DBN, I may want the ability to easily disconnect one end of the lead and I see flexible as the way to do that.

73 Andrew

Re: Help with SMA leads

G8TZJ
 

Thanks for the suggestions. I will look at these web sites and see who can provide the most suitable leads. In reply to G4DBN, I may want the ability to easily disconnect one end of the lead and I see flexible as the way to do that.

73 Andrew

Re: PE1RKI 23 Cm Low loss filter responce

Pete - GM4BYF
 

From Phils picture, I think Bert did understand your question. Guestimating from the grid there appears to be very little roll off between 1268 and 1296.

I wonder what your problems were on field day ? Transmit or receive or both?

73
Pete GM4BYF

On 11/07/19 19:12, Phil Guttridge G3TCU wrote:
Hi Simon,

I bought a 23cm filter from Bert earlier this year and he sent me this
link. It doesn't show a lot of detail on the spectrum axis but it might
be some guide.

https://www.flickr.com/photos/pe1rki/23099962502/in/album-72157658763409636/

73, Phil G3TCU

On 11/07/2019 18:33, simonchettle via Groups.Io wrote:
Hi All
I am thinking of using a 28 Mhz to 1296 transverter as part of a
Station re-build ( after poor result on VHD NFD!).
However I do not know the passband  rejection of the above filter at
1268 Mhz.  I have mailed Bert and he has replied the loss / rejection
is 0.99 dB – I think he slightly misunderstood  my question to him.
Has anybody measured the rejection at 1268 of one of his filters?  His
current web site does not appear to display the filter response and I
am sure it used to.
Cheers
Simon G8ATB

<http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient&utm_term=oa-4885-a>
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--
vry 73
Pete GM4BYF

Re: PE1RKI 23 Cm Low loss filter responce

Phil Guttridge G3TCU
 

Hi Simon,

I bought a 23cm filter from Bert earlier this year and he sent me this
link. It doesn't show a lot of detail on the spectrum axis but it might
be some guide.

https://www.flickr.com/photos/pe1rki/23099962502/in/album-72157658763409636/

73, Phil G3TCU

On 11/07/2019 18:33, simonchettle via Groups.Io wrote:
Hi All
I am thinking of using a 28 Mhz to 1296 transverter as part of a
Station re-build ( after poor result on VHD NFD!).
However I do not know the passband  rejection of the above filter at 
1268 Mhz.  I have mailed Bert and he has replied the loss / rejection
is 0.99 dB – I think he slightly misunderstood  my question to him.
Has anybody measured the rejection at 1268 of one of his filters?  His
current web site does not appear to display the filter response and I
am sure it used to.
Cheers
Simon G8ATB

<http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient&utm_term=oa-4885-a>
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<#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>

PE1RKI 23 Cm Low loss filter responce

simonchettle
 

Hi All
 
I am thinking of using a 28 Mhz to 1296 transverter as part of a Station re-build ( after poor result on VHD NFD!).
 
However I do not know the passband  rejection of the above filter at  1268 Mhz.  I have mailed Bert and he has replied the loss / rejection is 0.99 dB – I think he slightly misunderstood  my question to him.
 
Has anybody measured the rejection at 1268 of one of his filters?  His current web site does not appear to display the filter response and I am sure it used to.
 
Cheers
Simon G8ATB
 

Re: Oscar 100 Photos

John E. Beech
 

Tnx John G7JTT,
I've added that image to my collection.

de John G8SEQ

-------Original Message-------
From: John <@G7JTT>
There was a tweet back in the first few weeks of the sat reaching it's
obit that showed a time lapse video that showed the stars streaming
past and the stationary white dots of Es'Hail 2 and its other sats in
the same orbit. Can't find the video but here is the still, sorry not
sure who was the original poster of this image.

all best John G7JTT

Re: Life Changing decision - NOT !

Paul G8KFW
 

Hi don’t shoot the messenger

 

But there was talk a long time ago to split  UK microwave group

In that an old Group name would be used to ,arrange contacts and competitions / field days  etcetera

Leaving UK microwave as just a Technical group

Such as   

UK microwave / Scatterpoint       (tecknical)

UK microwave / SHF                  (arrange contacts and competitions / field days  etcetera)

UK HF                                      (tecknical DC to 30 Mhz )

 

Just a thought

 


From: UKMicrowaves@groups.io [mailto:UKMicrowaves@groups.io] On Behalf Of Andy G4JNT
Sent: 10 July 2019 18:33
To: UK Microwaves groups.io
Subject: Re: [UKMicrowaves] Life Changing decision - NOT !

 

You may well be right.

 

But I am chairman of the RSGB Technical Forum - where RSGBTech actually originated, but got separated - and I'd like to get that link back.  But those suggested names do appeal

 

Can't do anything for a month or so, anyway

 

Andy

 

 

 

Virus-free. www.avg.com

 

On Wed, 10 Jul 2019 at 18:28, Martin - G8JNJ via Groups.Io <martin_ehrenfried=yahoo.com@groups.io> wrote:

On Tue, Jul 9, 2019 at 10:05 PM, Andy G4JNT wrote:

I have just quit the RSGBTechnical Group - after getting a message bounced by the moderator (drifting off topic or something like that).  But it was getting inane and boring most of the time, anyway.

Why not start a new IO group ?

Amateur radio technology / Amateur radio workshop or similar ?

I think the RSGB part of RSGB Tech is off-putting to non members and overseas experimenters, and my experience is that it's not really associated with the RSGB anyway.

Regards,

Martin - G8JNJ

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--
Paul Bicknell G8KFW   South Coast UK

Re: Life Changing decision - NOT !

Mike Willis
 

The RSGB part is also bordering on fraudulent, at the least very misleading as it is not an RSGB managed group.
--
Mike G0MJW

Re: Life Changing decision - NOT !

Andy G4JNT
 

OK all, nothing can happen here for a few weeks.  
 I'll probably do something by September
Lets finish with the subject on this Group now - it's not microwaves, after all.
 


Virus-free. www.avg.com


On Wed, 10 Jul 2019 at 19:28, Tim Hague M0AFJ via Groups.Io <m0afj=yahoo.co.uk@groups.io> wrote:
I would also support that along with Dave G8KBV

Best Regards
Tim Hague


On 10 Jul 2019, at 19:16, Frank, G0GSR <frank.g0gsr@...> wrote:

On Wed, Jul 10, 2019 at 06:28 PM, Martin - G8JNJ wrote:
Why not start a new IO group ?

Amateur radio technology / Amateur radio workshop or similar ?
I would certainly support that.

Frank, g0gsr

Re: Life Changing decision - NOT !

Tim Hague M0AFJ
 

I would also support that along with Dave G8KBV

Best Regards
Tim Hague


On 10 Jul 2019, at 19:16, Frank, G0GSR <frank.g0gsr@...> wrote:

On Wed, Jul 10, 2019 at 06:28 PM, Martin - G8JNJ wrote:
Why not start a new IO group ?

Amateur radio technology / Amateur radio workshop or similar ?
I would certainly support that.

Frank, g0gsr

Re: Portable ops.. battery?

Andy
 

Ben, if you buy LiPo / LiFePo batteries from the bigger dealers you will
not have insurmountable problems. Companies such as Hobbyking are easy
to deal with, ship batteries inline with recommended best practices and
honour the warranties. Batteries from Zippy and Turnigy are normally top
notch when bought from people like Hobbyking. But like everything
nowadays, there are plenty of counterfeits on sale. Caveat emptor.

Whilst there's no guarantee any of these batteries wont fail under
warranty, there's plenty of good reports in the HF portable community of
Hobbyking replacing or refunding warranty failures.

Use your common sense and pay with a credit card so you can claim from
the card company (section 75 Consumer Credit Act I think) if you do get
stuck with a dealer not wanting to play ball.

There appears to be a bit of worldwide shortage of RC model LiFePo packs
at present. LiPo packs seem no problem. You can also look at building
packs out of 18650 sized cells. The RC model group websites are a good
source of ideas.

AFAIK LiFePo packs are much safer and a lower fire risk. Normally it's
physical damage or incorrect discharge/charge that causes fires.

Andy

On 10/07/2019 13:16, militaryoperator via Groups.Io wrote:
Subject: Re: [UKMicrowaves] Portable ops.. battery?


Ben,
I only operate portable and use either a LiPo with a bridge rectifier as
a dropper.
(the pack is a Turnigy Graphene 10000mAh 4S1P 15C)
or
a LiFePo4 without voltage reduction. (Zippy Flightmax 4200mAh 4S2P 30C)
Both are available from Hobbyking.
I believe the LiFePo4 is the safer option, but not available in the
larger sizes.

73
Stuart


WOW, that Turny batt is £885 on ebay!! but only £87 on Hobbyking!!  One
hell of a portable supply, hi.

I get the idea so thanks for the pointer,

cheers, Ben.

Re: Life Changing decision - NOT !

Frank, G0GSR
 

On Wed, Jul 10, 2019 at 06:28 PM, Martin - G8JNJ wrote:
Why not start a new IO group ?

Amateur radio technology / Amateur radio workshop or similar ?
I would certainly support that.

Frank, g0gsr

Re: Life Changing decision - NOT !

Andy G4JNT
 

You may well be right.

But I am chairman of the RSGB Technical Forum - where RSGBTech actually originated, but got separated - and I'd like to get that link back.  But those suggested names do appeal

Can't do anything for a month or so, anyway



Virus-free. www.avg.com


On Wed, 10 Jul 2019 at 18:28, Martin - G8JNJ via Groups.Io <martin_ehrenfried=yahoo.com@groups.io> wrote:
On Tue, Jul 9, 2019 at 10:05 PM, Andy G4JNT wrote:
I have just quit the RSGBTechnical Group - after getting a message bounced by the moderator (drifting off topic or something like that).  But it was getting inane and boring most of the time, anyway.
Why not start a new IO group ?

Amateur radio technology / Amateur radio workshop or similar ?

I think the RSGB part of RSGB Tech is off-putting to non members and overseas experimenters, and my experience is that it's not really associated with the RSGB anyway.

Regards,

Martin - G8JNJ

Re: Life Changing decision - NOT !

Martin - G8JNJ
 

On Tue, Jul 9, 2019 at 10:05 PM, Andy G4JNT wrote:
I have just quit the RSGBTechnical Group - after getting a message bounced by the moderator (drifting off topic or something like that).  But it was getting inane and boring most of the time, anyway.
Why not start a new IO group ?

Amateur radio technology / Amateur radio workshop or similar ?

I think the RSGB part of RSGB Tech is off-putting to non members and overseas experimenters, and my experience is that it's not really associated with the RSGB anyway.

Regards,

Martin - G8JNJ

Re: Portable ops.. battery?

Bill, G4CUE
 

Dear Ben,

Lead-acid ones have the best price/capacity ratio but, of course, they
are heavy! If that's not a problem, I suggest looking at:

https://www.tayna.co.uk/

They have a huge range and also sell a few lithium types, for example:

https://www.tayna.co.uk/leisure-batteries/lifos/

I've always had good service from them.

Best wishes,

Bill.

Tuesday, July 9, 2019, 5:02:11 PM, you wrote:

Any recommendations re battery for portable ops?
Leisure battery etc? Halfords has 12v 70Ah and 115Ah ones and of course, loads on the bay.
Or better to go lipo etc, some 7.4v 5.2Ah ones in series parallel
to give a good 13.8v via a diode feed?

Ben.





Re: Life Changing decision - NOT !

Mike Willis
 

I think you mean last month as August issue arrived today. It's an antenna special and it has got almost nothing of interest in it.

Winging from HF types about noise expecting to be support from Ofcom, two what I did on my holidays expedition reports, Airfields on the air, Cricket fans on the air, Mills on the air.... HF antennas that look like they have been designed to upset the neighbours. One small technical piece on microwaves and a couple of interesting columns by Andy. 

Meanwhile, lots going on in UHF, microwaves, satellites, SDR and all sorts of design innovation that doesn't get a look in. It's no wonder many administrations don't see the need to amateur radio these days.
--
Mike G0MJW