Date   

Re: attenuator

Gordon REASON <gordonj.reason@...>
 

Looking at an online attenuator calculator , for a Pi style , fo 50 Ohms .........                                                         some 52 ohms to ground at each end , and 789 ohms across the top ...........

So , a choice ......... it's either been fried ........ or the label has been changed .........

Do you have a Vna , to check it with ?

On 05 March 2021 at 12:01 "militaryoperator via groups.io" <Military1944@...> wrote:

I have this 100W 30db attenuator but the i/p measures 14 ohms to gnd, the o/p 51 ohm to gnd and the through is 61 ohm. 

I'm thinking its duff? 

Ben


GB3OSW

Martyn G3UKV
 

Welcome back beacon GB3OSW (IO82KV80) on 3cm - 10368.780 MHz.
Not many spotters so far on beaconspot.uk - so have a listen if possible.
Thanks Peter (G3SMT - beacon NoV).
73 Martyn G3UKV

Virus-free. www.avg.com


attenuator

militaryoperator
 

I have this 100W 30db attenuator but the i/p measures 14 ohms to gnd, the o/p 51 ohm to gnd and the through is 61 ohm. 

I'm thinking its duff? 

Ben


Nano VNA SAA-2N and G3XDY QRO filter

david656179
 

Just finished the 2nd filter, these 0603 components are tricky and can fly long distances !!

Note to say that by setting different calibrated ranges for 1296 - 2592 and 3888 MHz on this VNA I was able to check the return loss at 1296 and tune for best dips at 2592 and 3888.  The point being that the VNA is listed as 3 GHz top frequency, mine appeared to go to 4 GHz.  Sure the readings might be inaccurate but if one is just tuning a filter for rejection, finding this extended range was a pleasant surprise.  I have not altered any of the firmware/software from purchase last Autumn, when I think i am right is saying John XDY, reported that there were several owners in the Ipswich area.  A remarkable unit for around £100 carriage paid.

David


Re: GB3MCB current frequency?

John Fell
 

Hi Neil,
GB3MCB is specified to use F1A keying .It does not have any digital add ons .

I do not think Brian G4NNS added any external locking to the LO , so periodic drift is probable .

I had a sniff from it in January this year , very short duration .At that time it was 10368.9685MHz - BeaconSpot lists a few other spots within 2 kHz of that area .

When I was last in GW , in Pembrokeshire 2019, it was a strong signal along the coast and its keying and short term stability  good .
In this direction (E) it has to get over the mass of Dartmoor , so I do not expect to hear it much , even though I had my West end Pine tree topped last week. .
I do not bother elevating my telescopic mast much but did in January "coz it felt right" kind of Tropogation - something that is in limited supply at the moment .
I have seen FNY more often !

With KBQ , CAM , RPE and effectively MHZ all QRT ,we could do with more Beacon sources on 10GHz .

What's occurring Chaps ?

73
John
G0API

On Thu, 4 Mar 2021 at 22:15, Neil Smith G4DBN <neil@...> wrote:

I'm seeing a very very weak trace on 10368.97056 MHz coming from the right direction to be GB3MCB. It is a little bit wobbly, by up to 10 Hz. It disappears when I beam away or elevate, but I don't see any obvious FSK.  I seem to remember that MCB used to have a very very narrow shift, and tended to bounce a bit during the keying cycles, but it is so long since I heard it last that I might be seeing something totally different.  Just seems concidence that the signal is in the right direction, and somewhere near the right frequency.  MCB is 460 km away, so no wonder it's weak, but this doesn't feel quite right.  Can anyone confirm what frequency MCB is on right now, and whether is is using A1A or something instead of FSK?

Neil G4DBN


Re: GB3MCB current frequency?

Neil Smith G4DBN
 

I don't think it is locked, and it is miles off frequency.  This is an old trace from it in 2019 when it was hugely stronger.  The trace at present only shows up on a 262144-length FFT in Spectrum Lab and as a faint trace in WSJT-X at max contrast, hardly anything on the DUO IF trace even with contrast maxed.  My end is locked to a free-running Morion MV89A that is tweaked manually to within 10 Hz or so at 10 GHz.

The signal level feels slightly too steady, not scintillating like I'd expect with troposcatter. Also, there are no obvious doppler tracks or smears from the very few planes on the path.

I'll have another look later and see if it is still there.  This is with a 95cm dish up at 13m, waveguide relay and waveguide LNA, clear to the horizon out to 73km in that direction, so it isn't totally impossible.

Neil G4DBN

On 04/03/2021 22:23, Andy G4JNT wrote:
10Hz random wobble on 10GHz over a period of tens of seconds is typical of a GPSDO
Is 'MCB GPSDO locked ?




Re: ICNIRP

Stephen Tompsett
 

Someone suggested that I try Office365 to open the spreadsheet; It doesn't work for me I get the following error message:

We're sorry. We can't open the workbook in the browser because it uses these unsupported features:
• Custom toolbar attached to the workbook (also called attached toolbar)


On 04/03/2021 20:30, Stephen Tompsett wrote:

Having persuaded the spreadsheet to work (partially), the calculated horizontal distances appear to be ridiculous for  high gain antennas. While it may be necessary to allow a significant distance in the direction a high gain antenna is transmitting, the same distance cannot be required behind or to the side of such an antenna, where I would expect the required distance to be comparable to the distance required for an isotropic radiator or the near field value?

On 04/03/2021 06:17, GM6VXB via groups.io wrote:
Watching this thread with interest and will not reply to comments.
Have done two RF safety courses in my commercial life so do understand what is
and is not safe to be close to RF wise.
Have looked at both the RSGB (who are they) and OFCOM 'calculators' which although
almost correct do not really take into account the duty cycles involved in amateur radio.

Martin, GM6VXB
-- 
Stephen Tompsett (G8LYB)
Tel: 01788 578940
Mob: 07956 855816
-- 
Stephen Tompsett


Re: GB3MCB current frequency?

Andy G4JNT
 

10Hz random wobble on 10GHz over a period of tens of seconds is typical of a GPSDO
Is 'MCB GPSDO locked ?



On Thu, 4 Mar 2021 at 22:15, Neil Smith G4DBN <neil@...> wrote:

I'm seeing a very very weak trace on 10368.97056 MHz coming from the right direction to be GB3MCB. It is a little bit wobbly, by up to 10 Hz. It disappears when I beam away or elevate, but I don't see any obvious FSK.  I seem to remember that MCB used to have a very very narrow shift, and tended to bounce a bit during the keying cycles, but it is so long since I heard it last that I might be seeing something totally different.  Just seems concidence that the signal is in the right direction, and somewhere near the right frequency.  MCB is 460 km away, so no wonder it's weak, but this doesn't feel quite right.  Can anyone confirm what frequency MCB is on right now, and whether is is using A1A or something instead of FSK?

Neil G4DBN


GB3MCB current frequency?

Neil Smith G4DBN
 

I'm seeing a very very weak trace on 10368.97056 MHz coming from the right direction to be GB3MCB. It is a little bit wobbly, by up to 10 Hz. It disappears when I beam away or elevate, but I don't see any obvious FSK.  I seem to remember that MCB used to have a very very narrow shift, and tended to bounce a bit during the keying cycles, but it is so long since I heard it last that I might be seeing something totally different.  Just seems concidence that the signal is in the right direction, and somewhere near the right frequency.  MCB is 460 km away, so no wonder it's weak, but this doesn't feel quite right.  Can anyone confirm what frequency MCB is on right now, and whether is is using A1A or something instead of FSK?

Neil G4DBN


Re: ICNIRP

Stephen Tompsett
 

Having persuaded the spreadsheet to work (partially), the calculated horizontal distances appear to be ridiculous for  high gain antennas. While it may be necessary to allow a significant distance in the direction a high gain antenna is transmitting, the same distance cannot be required behind or to the side of such an antenna, where I would expect the required distance to be comparable to the distance required for an isotropic radiator or the near field value?

On 04/03/2021 06:17, GM6VXB via groups.io wrote:
Watching this thread with interest and will not reply to comments.
Have done two RF safety courses in my commercial life so do understand what is
and is not safe to be close to RF wise.
Have looked at both the RSGB (who are they) and OFCOM 'calculators' which although
almost correct do not really take into account the duty cycles involved in amateur radio.

Martin, GM6VXB
-- 
Stephen Tompsett (G8LYB)
Tel: 01788 578940
Mob: 07956 855816


Re: Wave guide dummy load.

Andy G4JNT
 

I'd have thought the uWave Column would be a better place.   

Is there really much interest in unknown quality loads in waveguide ?



On Thu, 4 Mar 2021 at 18:28, Greg - ZL3IX <zl3ix@...> wrote:
Since few of us will have a copy going so far back, how about repeating the design in RadCom. An idea for Design Notes, Andy (JNT)....?


Re: Wave guide dummy load.

Greg - ZL3IX
 

Since few of us will have a copy going so far back, how about repeating the design in RadCom. An idea for Design Notes, Andy (JNT)....?


Re: Bodgers Guide to Patio Moonbounce

John Fell
 

Interesting talk notes from John.
My olde school was Leeds Grammar  , which was just up the road from the fruit Salads - we were the Banana skins (Yellow cross on the cap) .Taught me how to swim , cricket and Rugby . Too young then for RF .

73
John
G0API 

On Thu, 4 Mar 2021 at 16:21, Dave G6HEF <hardknottdave@...> wrote:

Following on from last nights discussions here is the rather interesting EME article by John Worsnop.

I'm hoping to be a notch more ambitious, but whether I'll get there or not remains to be seen.

Bodger's Guide to Patio Moonbounce

Now all I need to do is remember what was advised re: interfacing a vibroplex bug with JT65b ;)


Re: ICNIRP

Dave G6HEF
 
Edited

"Political comments on this uWave Group  OM :-)"

I'd like to think it's clever satirical comedy. There are always crazy things at both ends of the spectrum. Same with EM radiation.


Ofcom -important message about your licence

Andy G4JNT
 




---------- Forwarded message ---------
From: John Rogers <m0jav@...>
Date: Thu, 4 Mar 2021 at 15:16
Subject: Ofcom -important message about your licence
To: Volunteer Leadership Team <LeadershipTeam@...>
Cc: Elaine Richards, G4LFM <Elaine.Richards@...>, Heather Parsons <heather.parsons@...>


Please use this information to respond to any questions you get on this topic:

 

-----------------

 

If you have received an email from Ofcom to your personal email address you will be aware of the new EMF area of their website: ofcom.org.uk/emf

 

Please direct people there if they have questions about the variation process and EMF conditions.  

 

The RSGB EMC Committee will share more information about assessments you can make over the coming weeks but they can’t reply to all individual queries at the moment.

 

If you didn’t receive an email, check your spam filter and ensure that Ofcom has your correct contact details. Please also encourage your club members to look for their copy of the email.

 

People should be aware that the RSGB information on EMF Exposure will be updated on rsgb.org.uk/emf

 

Tell people not to panic they have at least until November (May 2022 for <10Mhz bands) before they need to comply with these requirements.

 

----------------

 

Regards and 73 de
John Rogers (M0JAV/NHS)
RSGB Director

E: m0jav@...
W: www.rsgb.org.uk
Follow us on Twitter: @theRSGB

Patron: HRH The Prince Philip, Duke of Edinburgh, KG, KT.
Registered Office: 3 Abbey Court, Fraser Road, Priory Business Park, Bedford MK44 3WH, UK 
RSGB was founded in 1913 and incorporated in 1926. Registered Number: 216431

The information in this internet email is copyright of the Radio Society of Great Britain (RSGB), confidential and is intended solely for the addressee(s). Access, copying, dissemination to or re-use of information in it to or by anyone else is unauthorised unless stated clearly at the top of the email. Any views expressed in this email are those of the individual sender, except where the sender specifically states these to be the views of the RSGB.

 

 

John Rogers
Radio Society of Great Britain
 
 
 

 

John Rogers

Radio Society of Great Britain

m0jav@...
rsgb.org/board

RSGB Newsfeed RSGB on Facebook RSGB on Twitter RSGB on YouTube
Patron: HRH The Prince Philip, Duke of Edinburgh, KG, KT.
Registered Office: 3 Abbey Court, Fraser Road, Priory Business Park, Bedford MK44 3WH, UK
RSGB was founded in 1913 and incorporated in 1926. Registered Number: 216431
The information in this internet email is copyright of the Radio Society of Great Britain (RSGB), confidential and is intended solely for the addressee(s). Access, copying, dissemination to or re-use of information in it to or by anyone else is unauthorised unless stated clearly at the top of the email. Any views expressed in this email are those of the individual sender, except where the sender specifically states these to be the views of the RSGB.



 


Re: microwave absorbent adhesive polymer?

Paul Evans W4/VP9KF
 

Conductivity between the back of the absorber and the metal chassis (or normally, inside of the lid) may not be important. Normally the absorber is used to stop reflections inside the box when the lid is on, not to absorb 'all' the emitted power.

Bet Gordon got through gobs of the 3140 and absorber material from 'next door' in Towcester.
--
73, Paul Evans G4BKI [VP9KF]


Re: microwave absorbent adhesive polymer?

SAM JEWELL
 

Andy,



I can't send a bodge like that out to paying customers!!!

:>Q


Sam





------ Original Message ------
From: "Andy G4JNT" <andy.g4jnt@...>
To: "UK Microwaves groups.io" <UKMicrowaves@groups.io>
Sent: Thursday, 4 Mar, 21 At 13:34
Subject: Re: [UKMicrowaves] microwave absorbent adhesive polymer?

Have you tried just taping over with magic Tape (*) ?
It really does work well

(*) Other thin plastic self adhesive tapes are available.



On Thu, 4 Mar 2021 at 13:31, Gordon REASON via groups.io <gordonj.reason=virgin.net@groups.io> wrote:

RTV 3140 was our favourite adhesive .............

On 04 March 2021 at 09:32 "SAM JEWELL via groups.io" <jewell=btinternet.com@groups.io> wrote:

I would like to echo that comment about finding suitable adhesive to use with the polyurethane/silicon absorber materials. I was given a few sheets of 'plain' absorber of the sort I use with my VLNA preamps. I have tried all sorts of adhesives, but none of them adhere properly and several of them caused the absorber sheet to curl up.
I went back to the self adhesive type, expensive as it is.

73 de Sam, G4DDK





On 4 Mar 2021, at 08:18, Dave G8KHU <david@...> wrote:

Neil
Before you order check with Mouser that their material has the pressure sensitive adhesisve tape option - the Mouser description just says mounting is "adhesive". Does that mean it's got the adhesive film or that you need adhesive to glue it in place? The Digikey version does at least says that the adhesive is non-conductive single sided so I'm assuming that this is the factory fitted adhesive sheet . The base number just referes to the material and the laird site lists the psa as an option - https://www.laird.com/products/microwave-absorbers/microwave-absorbing-elastomers-and-films/eccosorb-mcs/21109145
The non-adhesive stuff is a pig for amateur use as nothing seems to stick it reliably, carpet tape falls off and superglue / rtv fail rapidly. The proper adhesive is a two part mix that's fiendishly expensive, comes in a one litre can which has very limited shelf life and has enough skull and crossbones warning symbols to sink a pirate ship. I had to use it once and swore never, ever, again.
HTH Dave G8KHU




Re: Eltek Flatpack2 PSU 3KW set to 48V or whatever you want.

Andy G4JNT
 

What inline fuse :-)
Don't see the point when you run things from PSUs with current limits / trips

Only two FETs blew out of the four, and by some fluke I had several devices spare in the junk box - must have anticipated blowing some.  So all repaired and I can have a linear 300 Watts on 137 & 475kHz kHz if needed.




On Thu, 4 Mar 2021 at 13:53, Mike Willis <willis.mj@...> wrote:
I suppose as long as you don't ask it to provide any more than 3kW it will be happy. For future reference I think you can set limits via the CAN Bus. Surprised your inline fuse didn't blow.
--
Mike G0MJW


Re: Pump up Masts

Clive Elliott GW4MBS
 

50kg head load looks useful, does it have a keyway I wonder?
--
Clive GW4MBS (ex-G8ADP)
Pottering on 6m - 3cm in a valley in IO71XW where any QSO is a triumph of optimism over geography!


Re: Pump up Masts

ian hope (2E0IJH)
 

Talk to Total Masts as that looks identical to the units they supply
 
Ian
M5IJH

 
 
Sent: Thursday, March 04, 2021 at 1:50 PM
From: "Mike Willis" <willis.mj@...>
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Pump up Masts
After some googling it looks very much like it is one of these with the compressor and valve accessories

http://www.nrentech.com/pneumatic-telescopic-mast/9m-SecurityCCTV-PneumaticTelescopicMast

--
Mike G0MJW

2641 - 2660 of 64011