Date   

Re: Input Needed for RadCom Column

John Worsnop
 

I should add that any GHz stuff that won't fit in to my 1 page will usually get in to Scatterpoint via me if you don't send it to editor@....

As I've said many times to people, if you want a larger GHz Bands column,  email radcom@... and ask for one. I'm happy to fill a second page.

As Elaine and Giles will tell you, every time I see them (the editors), I ask them for a second page, but the reply is the same.
"The readership doesn't demand it, "our recent survey" showed that GHz Bands is not widely read and was a minority interest....... but you can always write us stand alone articles" (Which I do!)

73

John   

On Tue, 21 Jan 2020 at 17:25, Andy G4JNT <andy.g4jnt@...> wrote:

Microwave input really ought to go in the uWaves / GHz column,  so John ought to get first dibs on anything.  But as I have three pages every month, and GHz has one, there's space for more so  ....................

It is getting more and more difficult to find interesting RF and Am. Radio related matters to write about for the regular three pages of Design Notes in RadCom every month.  'JNT labs own projects are running out of steam, and to be quite brutal about things, I personally am getting less and less interested in RF related matters altogether.   What interest remains is purely software / DSP and non radio related electronics.  Very little of which will form DN-suitable material.  

SO........

It really would help if I had input from readers.  What are you doing, bright ideas, helpful tips and hints etc.   Pat Hawker's old column, Tech Topics was made up entirely from reader input and stuff blatantly culled from other publications.   The latter is now pointless with 't web and I'm not even going tp consider that route.   So that leaves reader input.

Please send me your input as and when.  Most reader input will be pasted in directly, with a minimum of editing for correctness / grammar etc.   And naturally you'll be credited.

 OR ......

Although it doesn't help with DN, consider writing up your work as a standalone article for RadCom (or ...Plus   or ...Basics)  .  That way you'll see your work in print and get paid for it.    


Input Needed for RadCom Column

Andy G4JNT
 


Microwave input really ought to go in the uWaves / GHz column,  so John ought to get first dibs on anything.  But as I have three pages every month, and GHz has one, there's space for more so  ....................

It is getting more and more difficult to find interesting RF and Am. Radio related matters to write about for the regular three pages of Design Notes in RadCom every month.  'JNT labs own projects are running out of steam, and to be quite brutal about things, I personally am getting less and less interested in RF related matters altogether.   What interest remains is purely software / DSP and non radio related electronics.  Very little of which will form DN-suitable material.  

SO........

It really would help if I had input from readers.  What are you doing, bright ideas, helpful tips and hints etc.   Pat Hawker's old column, Tech Topics was made up entirely from reader input and stuff blatantly culled from other publications.   The latter is now pointless with 't web and I'm not even going tp consider that route.   So that leaves reader input.

Please send me your input as and when.  Most reader input will be pasted in directly, with a minimum of editing for correctness / grammar etc.   And naturally you'll be credited.

 OR ......

Although it doesn't help with DN, consider writing up your work as a standalone article for RadCom (or ...Plus   or ...Basics)  .  That way you'll see your work in print and get paid for it.    


Midland RT & Heelweg

Roger Ray
 

Input for Scatterpoint

Does anyone have a report and or pictures from the Midland Round Table, and Heelweg?

Thanks

Roger


Re: Dishes and wind

Paul Randall G3NJV
 

I think that picture shows the elevation actuator has been removed.
Paul


From: UKMicrowaves@groups.io <UKMicrowaves@groups.io> on behalf of Alan Beard <beardal@...>
Sent: 16 January 2020 10:00
To: UKMicrowaves@groups.io <UKMicrowaves@groups.io>
Subject: Re: [UKMicrowaves] Dishes and wind
 
Taken on Ponape, Federated States of Melanesia 

What happens if the wind blows the wrong way???

Taken in 2010

Alan VK2ZIW

On Wed, 15 Jan 2020 10:24:03 +0000, alwyn.seeds1 wrote
> The same Husband & Co. that did the structural design for Jodrell Bank.
>

> Interesting description of the issues faced in [UTF-8?]Lovell’s book [UTF-8?]“The Story of Jodrell [UTF-8?]Bank�.
>

> Regards,
>

> Alwyn

>
> _____________________________________________________
>

> Alwyn Seeds, Director
SynOptika Ltd.,
114 Beaufort Street,
London,
SW3 6BU,
England.


SynOptika Ltd., Registered in England and Wales: No. 04606737
Registered Office: 114 Beaufort Street, London, SW3 6BU, United Kingdom.
> _____________________________________________________


---------------------------------------------------
Alan Beard

OpenWebMail 2.53


Re: 13cms operation

Neil Smith G4DBN
 

Thanks for the reminder that the 2300 MHz NoVs need renewing after 3 years.  Mine was due to run out, so I renewed it.  You just need your licence reference number and details of any /P locations you intend to use.

Neil G4DBN

On 21/01/2020 13:13, Murray Niman wrote:

Hi Stuart

>"The UK Amateur Licence Schedules have a number of designated zones where restrictions apply"
Please read Schedule-2 of your Licence - the map is what that table is when you plot it!

More uptodate mapping guidance is on
https://rsgb.org/main/operating/licensing-novs-visitors/uk-licensing/guidance-resources/

 Murray G6JYB
-- 
Neil
<a href="http://g4dbn.uk/"><small>g4dbn.uk</small></a>


Re: 13cms operation

Murray Niman
 


Hi Stuart

>"The UK Amateur Licence Schedules have a number of designated zones where restrictions apply"
Please read Schedule-2 of your Licence - the map is what that table is when you plot it!

More uptodate mapping guidance is on
https://rsgb.org/main/operating/licensing-novs-visitors/uk-licensing/guidance-resources/

 Murray G6JYB


Re: FT290-490 mic

Paul G8AQA
 

On 20/01/2020 16:54, Chris Bartram G4DGU wrote:
Thanks for all the interest folks. As I suggested in my original email, the microphone has gone to the first person to get their address to me ...

There is clearly a market for microphones for the 290/790!

73

Chris

G4DGU




Re: 13cms operation

Stuart G1ZAR
 

On a similar line to the OP.
I shall soon be moving house and the new QTH will be in an area covered by one of the restricted zones.
"The UK Amateur Licence Schedules have a number of designated zones where restrictions apply"

https://www.microwavers.org/maps/license.htm

I have read through a version of the schedule downloaded from Ofcom, but cannot find the information on these (apart from Charing Cross).
Where can I find the required info, and could some further guidance or links be added to the map?
e.g. Charing cross states 431-432MHz 100km radius on the map, but the others only show grid ref and locator.

thank you
Stuart
G1ZAR


Re: Using a HP8484A with HP436a

Lou Blasco
 

Hi All,

I couldn't wait until the weekend so got out early this morning to see what was going on with the 436. Short story, one of the op-amps on the AC gain board was dead, output stuck low. U4 is a NS1826-0161 which can be replaced with a LM324. Bit of an anti-climax really, the meter just works as expected. 

For those that enjoy troubleshooting, U4A pin 1 was the culprit and as it happens is the only bit in a 4 bit word that needs to change to select a -20dBm sensor instead of a +20dBm sensor. They use the op-amp to generate these 4 bits by using different value resistors in the sensors to cover 10uW to 100W sensors. Quite ingenious really. The four bits feed high order bits of a ROM to do the range selection.

Thanks to all that responded, it was an interesting exercise.


image.png
 
Regards

Lou
VK3ALB


On Mon, Jan 20, 2020 at 10:53 PM Lou Blasco via Groups.Io <vk3alb=gmail.com@groups.io> wrote:
Hi Rainer,

Indeed not all the pins exist in this particular cable. Whilst there is good continuity on all wires there is only one ground wire (F) in this particular assembly and pins A, M, J are missing. The 10K sensor resistance can be measured between pins K and F. This evening I took the cable and sensor to a friend's house and confirmed they both work as expected in his 436. As the sensor resistor is detected in my friend's 436 and my 8901 I am confident that the issue lies in my 436. It's late in the evening here and no time to tear down the meter. I will have more time on the weekend to tackle this problem. Thanks for your interest and investigations and thanks to those of you that have replied so far. I will update everyone when I have more.
 
Regards

Lou
VK3ALB


On Mon, Jan 20, 2020 at 9:58 PM DF6NA Rainer <df6na@...> wrote:
Hi Lou,

the cables for the 435A are not wired on all PINs ! When you use such cable the 436A can not detect the sensor.
You need ALL Pins connected. You can check K, A, F, M, J with an OHM-Meter.

73, Rainer

Am 19.01.2020 um 22:32 schrieb Lou Blasco:
Hi Rainer,

I am using the same 11730A cable for both meters. Whilst not specifically mentioned in the 435 or 436 manuals I assume the variations in 11730 (A thru F) are simply cable length. Both manuals also lists the HP8484A so I assume that these suitable for use with either meter. Additionally, the cable and probes all work as expected with the HP435 so I'm leaning towards some kind of issue with the meter - either fault or limitation. 

Regards

Lou
VK3ALB


On Mon, Jan 20, 2020 at 8:09 AM DF6NA Rainer <df6na@...> wrote:
Hi,

you don't say what cable you are using. I guess it's the wrong cable for the 436A and the 436A thinks it has a different head!

73, Rainer


Am 19.01.2020 um 21:55 schrieb Lou Blasco:
Hi all,

I was trying to use a 8484A sensor with my 436a and found an anomaly. The issue is the reference cal reads +10dBm instead of 0dBm. 

My presumption is that either the meter cannot deal with the sensor correctly or there is something wrong with my meter. I have an 8481 and 8482 sensor which both behave correctly with the 436a.  I think my tests below point towards the an issue of some kind with the meter.

Haven't found anything on Google to confirm it but perhaps someone here with the same kit might be kind enough to check what I see.   

HP8484A connected to 11708A ref attenuator connected to the HP435 and it's internal reference reads -30dBm full scale.

HP8484A connected to 11708A ref attenuator connected to the HP435 and the 436 internal reference reads -30dBm full scale. 

HP8484A connected to 11708A ref attenuator connected to the HP436 and it's internal reference reads +10dBm. 

HP8484A connected to 11708A ref attenuator connected to the HP436 and the 435 internal reference reads +10dBm.

Regards

Lou
VK3ALB



Re: 13cms operation

Murray Niman
 

The RSGB online bandplan has this detail too
https://rsgb.org/main/operating/band-plans/microwaves/spectrum-release/

Further sharing has occurred since, so we do try to be careful in 13cm

73

   Murray G6JYB 


Re: 13cms operation

John Quarmby
 

Hi Ed


See this document:

https://www.ofcom.org.uk/__data/assets/pdf_file/0025/79810/pssr_amateur_statement.pdf


In particular section 5, and para 5.34 on page 36


73


John G3XDY


On 20/01/2020 21:43, Ed G3VPF wrote:
As a newcomer to 13cms I am somewhat confused by the recently published contest rules for Microwave Group contests. I understand the need for an NoV to operate on 2300MHz, but don't understand the need to supply Ofcom with a long list of information for operation on 2320MHz. I checked the Ofcom website which does not show this requirement in the licence schedule, and the RSGB bandplan which also does not show this requirement.

Have I missed something?

Ed G3VPF IO80RQ


13cms operation

Ed G3VPF
 

As a newcomer to 13cms I am somewhat confused by the recently published contest rules for Microwave Group contests. I understand the need for an NoV to operate on 2300MHz, but don't understand the need to supply Ofcom with a long list of information for operation on 2320MHz. I checked the Ofcom website which does not show this requirement in the licence schedule, and the RSGB bandplan which also does not show this requirement.

Have I missed something?

Ed G3VPF IO80RQ


Trimble ACE III GPS receivers

Andy
 

I'm de-cluttering the shack and have found a few Trimble ACE III GPS
receivers that were removed from old working equipment equipment. Whilst
they are quite mature, they were working, have 1PPS output, NMEA serial
sentences etc. as well as an external antenna socket

Are these of any real value or should I just bung them on eBay and see
what happens?

Andy
MM0FMF


FT290-490 mic

Chris Bartram G4DGU
 

Thanks for all the interest folks. As I suggested in my original email, the microphone has gone to the first person to get their address to me ...

There is clearly a market for microphones for the 290/790!

73

Chris

G4DGU


Re: Antique FT290/790 mic.

Adrian G4UVZ
 

I still use the 290 for 10G Chris and have had the mic capsule fail....It would therefore be much appreciated.

I think you have my address?

A


Re: Using a HP8484A with HP436a

Lou Blasco
 

G'day Doug,

Yes agreed with your assessment and that's why I made an effort to chase down an 8484A. This particular sensor behaves very well down to -65dBm and is still good at -69dBm. At -70 the reading starts to move around a bit but I think that's plenty of range for amateur work. Thanks for your comments.

Regards

Lou
VK3ALB


On Mon, Jan 20, 2020 at 10:17 PM DougF VK4OE <uwaves@...> wrote:
Greetings to all readers!

Indeed, the sensitivity of the '8484 sensor is too great for the
'normal' measurements that UHF and microwave radio amateurs are likely
to perform, and the use of a 40 dB attenuator brings the '8484 into line
with the '8481, '8485 and '8487 sensors.

But don't forget that there are some practical situations where the
extra sensitivity comes in very handy.  I am thinking of return loss
measurements of devices where you're using only around 0 to +10 dBm of
leveled incident power from the likes of typical signal generators,
working through, say, a -20 dB directional coupler (chosen for better
directivity) and where the RL is actually pretty good, say better than
-20 dB.  The '8484 allows full scale meter deflections whereas you're
only left guessing when attempting to use, say, an '8481 in the same
situation.

Another situation, related to that one, could be in the assessment of
amplifier input return loss where you purposely have chosen to perform
the measurement at a reduced power level, say around -20 or -30 dBm.

Yet another situation where I have found the increased sensitivity of
the '8484 to be valuable is in determining the directivity of a
directional coupler when the base coupling level is in the -20 db to -30
dB range, always making sure, of course, that you have a test load whose
return loss is very good!

I enjoy the situation where I have both types of power sensor in my
shack/lab, each with its own '435B power meter.  And they're still
amazingly reliable test instruments even after 30+ years since manufacture!

Best 73,

--Doug Friend, VK4OE.





Re: Using a HP8484A with HP436a

Lou Blasco
 

Hi Rainer,

Indeed not all the pins exist in this particular cable. Whilst there is good continuity on all wires there is only one ground wire (F) in this particular assembly and pins A, M, J are missing. The 10K sensor resistance can be measured between pins K and F. This evening I took the cable and sensor to a friend's house and confirmed they both work as expected in his 436. As the sensor resistor is detected in my friend's 436 and my 8901 I am confident that the issue lies in my 436. It's late in the evening here and no time to tear down the meter. I will have more time on the weekend to tackle this problem. Thanks for your interest and investigations and thanks to those of you that have replied so far. I will update everyone when I have more.
 
Regards

Lou
VK3ALB


On Mon, Jan 20, 2020 at 9:58 PM DF6NA Rainer <df6na@...> wrote:
Hi Lou,

the cables for the 435A are not wired on all PINs ! When you use such cable the 436A can not detect the sensor.
You need ALL Pins connected. You can check K, A, F, M, J with an OHM-Meter.

73, Rainer

Am 19.01.2020 um 22:32 schrieb Lou Blasco:
Hi Rainer,

I am using the same 11730A cable for both meters. Whilst not specifically mentioned in the 435 or 436 manuals I assume the variations in 11730 (A thru F) are simply cable length. Both manuals also lists the HP8484A so I assume that these suitable for use with either meter. Additionally, the cable and probes all work as expected with the HP435 so I'm leaning towards some kind of issue with the meter - either fault or limitation. 

Regards

Lou
VK3ALB


On Mon, Jan 20, 2020 at 8:09 AM DF6NA Rainer <df6na@...> wrote:
Hi,

you don't say what cable you are using. I guess it's the wrong cable for the 436A and the 436A thinks it has a different head!

73, Rainer


Am 19.01.2020 um 21:55 schrieb Lou Blasco:
Hi all,

I was trying to use a 8484A sensor with my 436a and found an anomaly. The issue is the reference cal reads +10dBm instead of 0dBm. 

My presumption is that either the meter cannot deal with the sensor correctly or there is something wrong with my meter. I have an 8481 and 8482 sensor which both behave correctly with the 436a.  I think my tests below point towards the an issue of some kind with the meter.

Haven't found anything on Google to confirm it but perhaps someone here with the same kit might be kind enough to check what I see.   

HP8484A connected to 11708A ref attenuator connected to the HP435 and it's internal reference reads -30dBm full scale.

HP8484A connected to 11708A ref attenuator connected to the HP435 and the 436 internal reference reads -30dBm full scale. 

HP8484A connected to 11708A ref attenuator connected to the HP436 and it's internal reference reads +10dBm. 

HP8484A connected to 11708A ref attenuator connected to the HP436 and the 435 internal reference reads +10dBm.

Regards

Lou
VK3ALB



Re: Using a HP8484A with HP436a

DougF VK4OE
 

Greetings to all readers!

Indeed, the sensitivity of the '8484 sensor is too great for the 'normal' measurements that UHF and microwave radio amateurs are likely to perform, and the use of a 40 dB attenuator brings the '8484 into line with the '8481, '8485 and '8487 sensors.

But don't forget that there are some practical situations where the extra sensitivity comes in very handy.  I am thinking of return loss measurements of devices where you're using only around 0 to +10 dBm of leveled incident power from the likes of typical signal generators, working through, say, a -20 dB directional coupler (chosen for better directivity) and where the RL is actually pretty good, say better than -20 dB.  The '8484 allows full scale meter deflections whereas you're only left guessing when attempting to use, say, an '8481 in the same situation.

Another situation, related to that one, could be in the assessment of amplifier input return loss where you purposely have chosen to perform the measurement at a reduced power level, say around -20 or -30 dBm.

Yet another situation where I have found the increased sensitivity of the '8484 to be valuable is in determining the directivity of a directional coupler when the base coupling level is in the -20 db to -30 dB range, always making sure, of course, that you have a test load whose return loss is very good!

I enjoy the situation where I have both types of power sensor in my shack/lab, each with its own '435B power meter.  And they're still amazingly reliable test instruments even after 30+ years since manufacture!

Best 73,

--Doug Friend, VK4OE.


Re: Using a HP8484A with HP436a

DF6NA Rainer
 

Hi Lou,

the cables for the 435A are not wired on all PINs ! When you use such cable the 436A can not detect the sensor.
You need ALL Pins connected. You can check K, A, F, M, J with an OHM-Meter.

73, Rainer

Am 19.01.2020 um 22:32 schrieb Lou Blasco:

Hi Rainer,

I am using the same 11730A cable for both meters. Whilst not specifically mentioned in the 435 or 436 manuals I assume the variations in 11730 (A thru F) are simply cable length. Both manuals also lists the HP8484A so I assume that these suitable for use with either meter. Additionally, the cable and probes all work as expected with the HP435 so I'm leaning towards some kind of issue with the meter - either fault or limitation. 

Regards

Lou
VK3ALB


On Mon, Jan 20, 2020 at 8:09 AM DF6NA Rainer <df6na@...> wrote:
Hi,

you don't say what cable you are using. I guess it's the wrong cable for the 436A and the 436A thinks it has a different head!

73, Rainer


Am 19.01.2020 um 21:55 schrieb Lou Blasco:
Hi all,

I was trying to use a 8484A sensor with my 436a and found an anomaly. The issue is the reference cal reads +10dBm instead of 0dBm. 

My presumption is that either the meter cannot deal with the sensor correctly or there is something wrong with my meter. I have an 8481 and 8482 sensor which both behave correctly with the 436a.  I think my tests below point towards the an issue of some kind with the meter.

Haven't found anything on Google to confirm it but perhaps someone here with the same kit might be kind enough to check what I see.   

HP8484A connected to 11708A ref attenuator connected to the HP435 and it's internal reference reads -30dBm full scale.

HP8484A connected to 11708A ref attenuator connected to the HP435 and the 436 internal reference reads -30dBm full scale. 

HP8484A connected to 11708A ref attenuator connected to the HP436 and it's internal reference reads +10dBm. 

HP8484A connected to 11708A ref attenuator connected to the HP436 and the 435 internal reference reads +10dBm.

Regards

Lou
VK3ALB



Re: Using a HP8484A with HP436a

Paul G8KFW
 

Hi Colin  I totally agree with you in that It doesn’t seem to be detecting the head sensitivity.

 

Paul

 


From: UKMicrowaves@groups.io [mailto:UKMicrowaves@groups.io] On Behalf Of Colin G4EML
Sent: 20 January 2020 01:01
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Using a HP8484A with HP436a

 

Hi Paul, 

 

That’s exactly what I have found. Unfortunately my scale is not the type that is reversible. But even if it was I probably wouldn’t use it. The sensitivity of the 8484 is really too high for regular use. I have a good 18GHz 40dB attenuator, so I will continue to use that and normal range scale. 

 

It sounds like Lou’s 436a is reading as if it has the 8483 head fitted. It doesn’t seem to be detecting the head sensitivity.

 

73 

Colin. 

 

 


On 20 Jan 2020, at 00:15, Paul G8KFW <paul@...> wrote:

Hi Colin

 

The difference between the 8484 power sensor and the 8485 is 40 dB

8484 power sensor max power is -20 dBm

8485 power sensor max power is +20 dBm  this being the normal rang of power meters  and can be bought for less than £150

 

The HP 435 power meters came with 2 types of knob the early one was all plastic and had a little wing to it that quiet often broke

If you have this type you can upgrade the front knob there should be plenty around for next to nothing

 

The later ones have a metal scale and just between the metal scale and the knob is a knurled ring if you have this one you are in the money

unscrew the knurled ring ante clock wise and you should find another scale plate and another scale on the back of the normal scale

 

The special 30 dB attenuator that is supplied with the 8484 sensor is specifically for 50 Mhz  and is not good at other frequencies as 30 dB

 

Regards Paul

 O


From: UKMicrowaves@groups.io [mailto:UKMicrowaves@groups.io] On Behalf Of Lou Blasco
Sent: 19 January 2020 23:29
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Using a HP8484A with HP436a

 

Hi Colin,

 

You've given me food for thought. I've always assumed the meter reading is absolute then done a little mental arithmetic to include whatever attenuation I've put in front of the sensor. This works with the 435, i.e. 0dBm from the reference through a 30dB attenuator should give me -30dBm which is exactly what I see on the 435. I do see how you use a 40dB attenuator to make direct readings using the various range scales of the 435. I can see the arithmetic to reach +10dBm from a -20dBm sensor but I don't understand why the meter is reading 40dB high.

 

######  STOP PRESS ######

 

I just remembered I have a HP8901B analyser which also handles these probes. Calibrating the 8484A probe using the 8901B reference gives me a reading of -30dBm. I now have two meters that read correctly with the 8484A probe and the 436 that seemingly has a reading error of 40dB.

 

The 436 is an auto-ranging digital power meter and I do not believe I can manually select ranges although there's a range hold button. I can see from the service manual that there is a set of comparators monitoring the mount resistor and these comparators drive a range selector ROM. I haven't quite got my head around how it works yet so will look at it tonight.

 

 

Regards

 

Lou

VK3ALB

 

On Mon, Jan 20, 2020 at 9:28 AM Colin G4EML <colin@...> wrote:


The 435a certainly can’t tell what head is fitted. Not sure about the 436a.

I don’t think you have anything wrong. The 8484a head is 40db more sensitive than the ‘normal’ heads. When a 435a meter was supplied with an 8484a, HP fitted a different knob with adjusted ranges.  If you use an 8484a on a standard 435a it needs a 40db attenuator in line to read correctly. I don’t know the 436a but it sounds like it is behaving the same. The HP calibration attenuator supplied with the 8484a is 30dB so I would expect to read +10dBm on the cal source.

I have a 435a with a 8484a and I always have to use it with a good 40dB attenuator to get correct readings.

Colin G4EML.

On 19 Jan 2020, at 21:32, Lou Blasco <vk3alb@...> wrote:

internal

No virus found in this message.
Checked by AVG - www.avg.com
Version: 2016.0.8048 / Virus Database: 4793/15886 - Release Date: 08/14/18
Internal Virus Database is out of date.


--
Paul Bicknell G8KFW   South Coast UK

No virus found in this message.
Checked by AVG - www.avg.com
Version: 2016.0.8048 / Virus Database: 4793/15886 - Release Date: 08/14/18
Internal Virus Database is out of date.


--
Paul Bicknell G8KFW   South Coast UK