Date   

Re: Crawley microwave round table

Andy G4JNT
 

And I could do one in parallel on a Bodgers's guide to a 10GHz Portable Beacon

Andy  G4JNT

On 10 July 2016 at 07:14, John Worsnop john@... [ukmicrowaves] <ukmicrowaves@...> wrote:
 

Hi Chris
If you're stuck for a talk I could probably put something together along the lines of "The Bodger's Guide to building a 24GHz beacon" based on my experience making  of GB3CAM and GB3PKT.
73
John

On 8 Jul 2016 08:39, "Chris G0FDZ chris@... [ukmicrowaves]" <ukmicrowaves@...> wrote:
 

Hi folks

Another reminder that the Crawley microwave round table takes place on
Sunday September the 18th at the usual venue. Since Derek G3GRO's
passing, the Crawley club have said that they are happy to continue
hosting the event as long as there is a demand for it. Unfortunately at
this time I still have no definite talks confirmed, and the future of
this event lies entirely in the users hands. It would be great shame to
have to abandon the event in the future due to lack of support, so
please do offer to help out in this area not leave it to others. You do
not have to be an 'expert' to give a talk. I feel very reluctant to ask
yet again those who have helped me in the past by giving talks on a
regular basis. Please contact me direct if you are able to help or
require any information.

Thanks and regards

Chris G0FDZ



Re: Crawley microwave round table

g4bao
 

Hi Chris
If you're stuck for a talk I could probably put something together along the lines of "The Bodger's Guide to building a 24GHz beacon" based on my experience making  of GB3CAM and GB3PKT.
73
John

On 8 Jul 2016 08:39, "Chris G0FDZ chris@... [ukmicrowaves]" <ukmicrowaves@...> wrote:
 

Hi folks

Another reminder that the Crawley microwave round table takes place on
Sunday September the 18th at the usual venue. Since Derek G3GRO's
passing, the Crawley club have said that they are happy to continue
hosting the event as long as there is a demand for it. Unfortunately at
this time I still have no definite talks confirmed, and the future of
this event lies entirely in the users hands. It would be great shame to
have to abandon the event in the future due to lack of support, so
please do offer to help out in this area not leave it to others. You do
not have to be an 'expert' to give a talk. I feel very reluctant to ask
yet again those who have helped me in the past by giving talks on a
regular basis. Please contact me direct if you are able to help or
require any information.

Thanks and regards

Chris G0FDZ


Re: Crawley microwave round table

Chris G0FDZ
 

Its the Crawley club HQ south of Crawley town.

Chris


On 10/07/2016 06:30, 'Simon Brown' simon@... [ukmicrowaves] wrote:
 

Chris,

 

What is the usual location?

 

Simon Brown, GK4ELI
http://sdr-radio.com

 

From: ukmicrowaves@... [mailto:ukmicrowaves@...]
Sent: 08 July 2016 08:39
To: UK microwaves
Subject: [ukmicrowaves] Crawley microwave round table

 

 

Hi folks

Another reminder that the Crawley microwave round table takes place on
Sunday September the 18th at the usual venue. Since Derek G3GRO's
passing, the Crawley club have said that they are happy to continue
hosting the event as long as there is a demand for it. Unfortunately at
this time I still have no definite talks confirmed, and the future of
this event lies entirely in the users hands. It would be great shame to
have to abandon the event in the future due to lack of support, so
please do offer to help out in this area not leave it to others. You do
not have to be an 'expert' to give a talk. I feel very reluctant to ask
yet again those who have helped me in the past by giving talks on a
regular basis. Please contact me direct if you are able to help or
require any information.

Thanks and regards

Chris G0FDZ

No virus found in this message.
Checked by AVG - www.avg.com
Version: 2016.0.7640 / Virus Database: 4613/12590 - Release Date: 07/10/16



Re: Crawley microwave round table

Simon Brown
 

Chris,

 

What is the usual location?

 

Simon Brown, GK4ELI
http://sdr-radio.com

 

From: ukmicrowaves@... [mailto:ukmicrowaves@...]
Sent: 08 July 2016 08:39
To: UK microwaves
Subject: [ukmicrowaves] Crawley microwave round table

 

 

Hi folks

Another reminder that the Crawley microwave round table takes place on
Sunday September the 18th at the usual venue. Since Derek G3GRO's
passing, the Crawley club have said that they are happy to continue
hosting the event as long as there is a demand for it. Unfortunately at
this time I still have no definite talks confirmed, and the future of
this event lies entirely in the users hands. It would be great shame to
have to abandon the event in the future due to lack of support, so
please do offer to help out in this area not leave it to others. You do
not have to be an 'expert' to give a talk. I feel very reluctant to ask
yet again those who have helped me in the past by giving talks on a
regular basis. Please contact me direct if you are able to help or
require any information.

Thanks and regards

Chris G0FDZ


G4BAO 23cm PA kits at Finningley

g4bao
 

I will have the have the last three 1296MHz 45W PA kits + ten 1296MHz 2.5W driver kits with me at Finningley tomorrow.

No plans for making any further 45W kits in the foreseeable future. so get them while you can!
 
First come first served at Special show price of £80 for the 45W and £20 for the 2.5W

see www.g4bao.com for details

73
John
  


Re: GPSDO and JT4G

John McCarthy
 

Thanks Andy just found the manual so will read up on all the parameters, just looking at the screen grab I think I'm right in saying that SEE was around -12db so still loads of margin left ! look forward to getting the Tx side up and running now and get a new personal best on the band.

Cheers John 


On Saturday, 9 July 2016, 20:50, "Andy Talbot andy.g4jnt@... [ukmicrowaves]" wrote:


 
Its all in the Manual, which you'll have in your installation directory and available via the Help menu.  I suggest you read it fully as it describes in very good detail exactly how to use the suite and how all the modes work.

But to quickly summarise :

Sync is an relative measure of how well the sync vector - consisting of half of the transmitted message , has been decoded.    It gives a rough indication of how many symbols may have been received correctly.  But its actual value means nothing.

dB is the received Signal to Noise ratio, normalised to a noise bandwidth of 2.5kHz.  The minimum value that JT4 will decode properly is in the region of  -22dB

DF is the tuning error in Hz.  (When you migrate from the old WSJT-10 to WSJT-X, this parameter will become obsolete as there will no longer be a "correct" tuning point

W is the width of the received signal in Hz (the width of the individual tones, not the whole signal span)     When frequency scattering (rain, tropo, aircraft) occurs to spread out the tones, this figure will show an increase.

Andy  G4JNT


On 9 July 2016 at 20:20, g7jtt@... [ukmicrowaves] <ukmicrowaves@...> wrote:
 
[Attachment(s) from g7jtt@... [ukmicrowaves] included below]
Hi all finally seem to have sorted out my GPSDO after a complete rebuild (thanks again to Noel for all your help), which now has a 10MHz crystal instead of the 5MHz doubled up to 10MHz. Anyway here is a quick video showing the 106.500MHz  scanning before it locks on 106.500MHz (the error of +/- is in the SDR which is being used to monitor the signal) https://youtu.be/Bbe0r9PNe-w . So with this now working I went out today with Noel G8GTZ to play with his NB-DATV kit but took the 3cm along to look at beacons and check the DB6NT stability now the GPSDO is working. The site we went to is a ridge that's to  the east  of Basingstoke not the best of sites but good to the west and north. So GB3SCX was found first and for once it wasn't 59 but about  53-54 at around 90km, then looked for GB3SEE but the path was blocked so managed to get a reflection off of Hannington ridge at about 51- 52 and lastly Just about managed to here GB3KBQ in the noise, I knew it was there but unable to decode the CW but at 139km was glad to hear it. So with SCX and SEE sending JT4G I rigged up the laptop and was able to receive signals from both even though SEE was way down in the noise (see screen grab), So my questions to those more familiar with JT modes what do the the numbers mean below the Sync, db, DT, DF and W mean and what should i be looking at getting to decode. Next on the list of "To Do's" is set up the FT-290 for Tx on JT4G to try and work some of those just out of reach stations.

73 John




Re: GPSDO and JT4G [1 Attachment]

Andy G4JNT
 

Its all in the Manual, which you'll have in your installation directory and available via the Help menu.  I suggest you read it fully as it describes in very good detail exactly how to use the suite and how all the modes work.

But to quickly summarise :

Sync is an relative measure of how well the sync vector - consisting of half of the transmitted message , has been decoded.    It gives a rough indication of how many symbols may have been received correctly.  But its actual value means nothing.

dB is the received Signal to Noise ratio, normalised to a noise bandwidth of 2.5kHz.  The minimum value that JT4 will decode properly is in the region of  -22dB

DF is the tuning error in Hz.  (When you migrate from the old WSJT-10 to WSJT-X, this parameter will become obsolete as there will no longer be a "correct" tuning point

W is the width of the received signal in Hz (the width of the individual tones, not the whole signal span)     When frequency scattering (rain, tropo, aircraft) occurs to spread out the tones, this figure will show an increase.

Andy  G4JNT


On 9 July 2016 at 20:20, g7jtt@... [ukmicrowaves] <ukmicrowaves@...> wrote:
 
[Attachment(s) from g7jtt@... [ukmicrowaves] included below]

Hi all finally seem to have sorted out my GPSDO after a complete rebuild (thanks again to Noel for all your help), which now has a 10MHz crystal instead of the 5MHz doubled up to 10MHz. Anyway here is a quick video showing the 106.500MHz  scanning before it locks on 106.500MHz (the error of +/- is in the SDR which is being used to monitor the signal) https://youtu.be/Bbe0r9PNe-w . So with this now working I went out today with Noel G8GTZ to play with his NB-DATV kit but took the 3cm along to look at beacons and check the DB6NT stability now the GPSDO is working. The site we went to is a ridge that's to  the east  of Basingstoke not the best of sites but good to the west and north. So GB3SCX was found first and for once it wasn't 59 but about  53-54 at around 90km, then looked for GB3SEE but the path was blocked so managed to get a reflection off of Hannington ridge at about 51- 52 and lastly Just about managed to here GB3KBQ in the noise, I knew it was there but unable to decode the CW but at 139km was glad to hear it. So with SCX and SEE sending JT4G I rigged up the laptop and was able to receive signals from both even though SEE was way down in the noise (see screen grab), So my questions to those more familiar with JT modes what do the the numbers mean below the Sync, db, DT, DF and W mean and what should i be looking at getting to decode. Next on the list of "To Do's" is set up the FT-290 for Tx on JT4G to try and work some of those just out of reach stations.


73 John



GPSDO and JT4G

John McCarthy
 

Hi all finally seem to have sorted out my GPSDO after a complete rebuild (thanks again to Noel for all your help), which now has a 10MHz crystal instead of the 5MHz doubled up to 10MHz. Anyway here is a quick video showing the 106.500MHz  scanning before it locks on 106.500MHz (the error of +/- is in the SDR which is being used to monitor the signal) https://youtu.be/Bbe0r9PNe-w . So with this now working I went out today with Noel G8GTZ to play with his NB-DATV kit but took the 3cm along to look at beacons and check the DB6NT stability now the GPSDO is working. The site we went to is a ridge that's to  the east  of Basingstoke not the best of sites but good to the west and north. So GB3SCX was found first and for once it wasn't 59 but about  53-54 at around 90km, then looked for GB3SEE but the path was blocked so managed to get a reflection off of Hannington ridge at about 51- 52 and lastly Just about managed to here GB3KBQ in the noise, I knew it was there but unable to decode the CW but at 139km was glad to hear it. So with SCX and SEE sending JT4G I rigged up the laptop and was able to receive signals from both even though SEE was way down in the noise (see screen grab), So my questions to those more familiar with JT modes what do the the numbers mean below the Sync, db, DT, DF and W mean and what should i be looking at getting to decode. Next on the list of "To Do's" is set up the FT-290 for Tx on JT4G to try and work some of those just out of reach stations.


73 John


Re: Smith Chart

Mark GM4ISM
 

I agree Brian,
the graphical rotating around real impedances away from the normalised value works well only for a limited  range of transformations.  It is particularly useful for determining the intermediate impedance for a single or double quaterwave transformer.
 
This was taught  on BBC Shortwave stations as a quick and easy way of matching  antennas  in the days before computers and vector network analysers became  everyday objects.  Even then the graphical method was frowned upon when it came to formal training on Smith Charts at the BBC.
 
The technique of shifting the iconocentre, if I recall came into its own when the iconocentre about which it was necessary to rotate was complex itself.  This makes normalising ‘difficult’ and the mathematics of correcting for  a rotation about a complex impedance became less difficult, relatively.
I don’t remember much about it  but the case that always came up in the exam ( this was taught at University) was for a coax to waveguide transition.
It made my brain hurt then and it has never been needed in anger in my 30+ years as a professional antenna engineer, which is why I have all but forgotten it.
 
Regards
Mark GM4ISM
 

Sent: Saturday, July 09, 2016 12:54 PM
Subject: [ukmicrowaves] Re: Smith Chart
 
 

Hi Andy, Barry and Mark,

I can see Mark's suggestion will be good enough for most practical
cases, but as I teach
this stuff I have to show the students how to do it "properly", ;-) . By
the time the correction
is done it sounds simpler to normalise!

73s
Brian GM8BJF.

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Transverter Interface

Andy G4JNT
 

Well, I must really be losing it in old age here...

A slightly earlier version of this FT817 (and similar) transverter  interface without the DC switching  was  written up and published in RadCom Dec 2013, page 60.

Which I'd completely forgotten about until now!     So perhaps just as well I didn't get round to writing-up the whole thing all over again!

Found the text for that and incorporated it into a new version, to be found at 

Andy  G4JNT


On 29 June 2016 at 08:42, Andy Talbot <andy.g4jnt@...> wrote:
Is it worth writing this up, or are there already commercial designs that people just plug-n-play with?

A single board transverter interface that connects low power transceivers such as FT817 (or that olde favourite. the IC202) with low power mixers.  Single bi-directional mixers or separate Tx/Rx are catered for.    It extracts the PTT signal superimposed on the transceiver RF, generates +VTx and +VRx voltages at a couple of amps switching capability, and uses PIN diodes to switch RF through an attenuator on Tx and straight though on Rx.   A PIN diode on the Tx path allows varying the Tx drive level with a  DC  control signal.  Not a relay in sight

All components available via the catalogue suppliers or Chipbank if you're prepared to substitute and experiment a bit.


Re: Smith Chart

Brian Flynn GM8BJF
 

Hi Andy, Barry and Mark,

I can see Mark's suggestion will be good enough for most practical cases, but as I teach
this stuff I have to show the students how to do it "properly", ;-) . By the time the correction
is done it sounds simpler to normalise!

73s
Brian GM8BJF.


Andrews TNC Connectors needed.

Christopher Bartram <cbartram@...>
 

I have a very good coax relay for the lower frequency bands, ie. 1.3 - 3.4GHz, and I want to use it in a new preamp for small antenna EME on 23. The snag is that it uses TNC connectors.

Now, I could use adaptors to type-N, but in a situation where, particularly on receive, I'll be scrabbling for every last 0.05dB of loss in this unit, the use of adaptors is not a good idea!

I'm looking for two connectors: TNC(m) to FSJ4-50. I'm quite happy to pay for these, so if you have some in your junk-box (I don''t mind at all if they've been used, providing they are complete) please get in touch!

Vy 73

Chris
GW4DGU


Re: Smith Chart

Barry Chambers
 

Brian

Yes, I would second your suggestion about renormalisation.

73

Barry, G8AGN
On 08/07/2016 11:52, 'brian.flynn@...' brian.flynn@... [ukmicrowaves] wrote:

 

Hi Andy,

I get involved in this a bit. I have always read off the
impedance/admittance and re-normalised. I have never come across the
procedure you suggest. I do this fairly regularly to design quarter wave
matching sections when the the impedances are not real.

73s

Brian, GM8BJF.
--



Re: Smith Chart

Andy G4JNT
 

The  reply below from Mark was sent direct  :

Which is, more-or-less, what I can now recall being shown all those years ago.   It works for quarter wave transformers
Honour is satisfied and it appears that route was only ever a quick approximation for an impedance that had a mostly real component.

So there isn't an exact way of doing it - I felt all along it wasn't possible as a 'correct' Smith chart procedure!  At least without renormalising.
Much prefer calculation and software for microwave design than the manual Smith chart of old.

Andy  G4JNT

>Andy
>sorry I cant reply to the list, I am away from home and don't have the correct email account set up
>In answer to the question, a slightly reserved yes
> simply place the rotation point  on the real axis   at the 50 ohm normalised value ( eg. rotate round 1.5 for 75 ohm >system on a 50 ohm chart)
> for  rotations that don't result in a large reactive transformed impedance this is really quite accurate (ie.1/4 wave >rotations and multiples of this)
>
>there is an increased error in both the displayed real and imaginary components with rotations further from the >centre and with those that result in points away from the real axis.
> there is a mathematical correction that can be applied, but that last time i looked at that was 35 years ago
> look up shifting the iconocentre
>
>hope that helps 
>Mark
 



On 8 July 2016 at 11:52, 'brian.flynn@...' brian.flynn@... [ukmicrowaves] <ukmicrowaves@...> wrote:
 

Hi Andy,

I get involved in this a bit. I have always read off the
impedance/admittance and re-normalised. I have never come across the
procedure you suggest. I do this fairly regularly to design quarter wave
matching sections when the the impedances are not real.

73s

Brian, GM8BJF.
--



Re: Smith Chart

Brian Flynn GM8BJF
 

Hi Andy,

I get involved in this a bit. I have always read off the impedance/admittance and re-normalised. I have never come across the procedure you suggest. I do this fairly regularly to design quarter wave matching sections when the the impedances are not real.

73s

Brian, GM8BJF.
--


Crawley microwave round table

Chris G0FDZ
 

Hi folks

Another reminder that the Crawley microwave round table takes place on Sunday September the 18th at the usual venue. Since Derek G3GRO's passing, the Crawley club have said that they are happy to continue hosting the event as long as there is a demand for it. Unfortunately at this time I still have no definite talks confirmed, and the future of this event lies entirely in the users hands. It would be great shame to have to abandon the event in the future due to lack of support, so please do offer to help out in this area not leave it to others. You do not have to be an 'expert' to give a talk. I feel very reluctant to ask yet again those who have helped me in the past by giving talks on a regular basis. Please contact me direct if you are able to help or require any information.

Thanks and regards

Chris G0FDZ


Re: Locking a 20-26GHz YIG oscillator

Andy G4JNT
 

continued...

There are usually two tuning coils on a YIG.   One main tuning coil has high inductance and wide tuning range.  Its high inductance limits tuning speed and loop bandwidth to a very low value if that were used inside the PLL. A few tens of Hz bandwidth and even that would require a high voltage and current coil driver stage.   Another small tuning coil allows fast modulation to be superimposed.

The usual way to use a YIG within a PLL is to pretune using the main coil via a manually adjusted pot type control or, more scientifically,  via  lookup table and D/A converter within the controller. Aim toi tune open-loop to withn a couple of MHz of the target.  Certainly well within the pulling range of the fast modulation coil.   The PLL works on the fast tuning coil which is typically a few 100uH inductance and can manage loop bandwidths in kHz region.

YIGs have inherently good far out phase noise, so you can get away with PLL loop bandwidths lower than you would for a traditional  VCO, as a start, try going for a couple of kHz, just to get outside audible effects listening to  a narrow tone.

If you can get hold of the May 2009  RadCom, I wrote about driving YIGs as part of PLLs in that issue.  See pages 41-42

Andy  G4JNT


On 8 July 2016 at 07:35, Andy Talbot <andy.g4jnt@...> wrote:
Try this, a new take on the old mixer-synth design :

Use one synth, perhaps an integer N design,  to make a locked source that simply  multiplies the reference to a frequency not too far from your wanted output.    Mix that with the YIG output to give an IF of say a few hundred MHz, even up to a couple of GHz.   Use this synth-mixer combination as a single entity, forming the VCO for a second synthesizer, driving the YIG control.

Either synth could be fract-N to give you your fine tuning; only one needs to be fixed frequency.

Andy  G4JNT



On 7 July 2016 at 23:29, Neil Smith G4DBN neil@... [ukmicrowaves] <ukmicrowaves@...> wrote:
 

I am playing with a 20-26.5GHz YIG oscillator. What is the received wisdom on the best way to use one of these as the VCO in a synth locked to a 10MHz standard?

I am building some LMX2582-based LO boards but I’d like to find a way to use the YIG for a source/LO on the mm bands.

Neil G4DBN




Re: Locking a 20-26GHz YIG oscillator

Andy G4JNT
 

Try this, a new take on the old mixer-synth design :

Use one synth, perhaps an integer N design,  to make a locked source that simply  multiplies the reference to a frequency not too far from your wanted output.    Mix that with the YIG output to give an IF of say a few hundred MHz, even up to a couple of GHz.   Use this synth-mixer combination as a single entity, forming the VCO for a second synthesizer, driving the YIG control.

Either synth could be fract-N to give you your fine tuning; only one needs to be fixed frequency.

Andy  G4JNT



On 7 July 2016 at 23:29, Neil Smith G4DBN neil@... [ukmicrowaves] <ukmicrowaves@...> wrote:
 

I am playing with a 20-26.5GHz YIG oscillator. What is the received wisdom on the best way to use one of these as the VCO in a synth locked to a 10MHz standard?

I am building some LMX2582-based LO boards but I’d like to find a way to use the YIG for a source/LO on the mm bands.

Neil G4DBN



Locking a 20-26GHz YIG oscillator

Neil Smith G4DBN
 

I am playing with a 20-26.5GHz YIG oscillator. What is the received wisdom on the best way to use one of these as the VCO in a synth locked to a 10MHz standard?

I am building some LMX2582-based LO boards but I’d like to find a way to use the YIG for a source/LO on the mm bands.

Neil G4DBN


Smith Chart

Andy G4JNT
 

Can anyone remember :

On a smith chart normalised to Zo, is it possible to move along a transmission line with a different characteristic impedance using a single (paper / pen / dividers compass) action?

And if so, what's the procedure?   I very vaguely recall someone doing it, but not too sure when / who / why / how

Or does the Smith chart have to be renormalised to the new Zo with the impedance recalculated and replotted?  

Andy  G4JNT