Date   

Re: 432MHz ATU?

Neil Smith G4DBN
 

If you can get hold of a VNA and see what the impedance looks like, you could make a two-stub tuner from coax. 6:1 sounds like the coax outer has corroded away or something, was the match ever OK, or has it always been off? Does it change across  the band? If so, what is the curve like?


A NanoVNA would illuminate the problem. Loads of examples of two-stub tuners out on the internet.

6:1 sounds like something disastrous though.


Neil G4DBN


On 15/02/2021 23:12, ian hope (2E0IJH) wrote:
 
Ian
M5IJH
 
 
Sent: Monday, February 15, 2021 at 11:03 PM
From: "g4zod@... via groups.io" <g4zod@...>
To: UKMicrowaves@groups.io
Subject: [UKMicrowaves] 432MHz ATU?

I have a long term problem with my 17 element MET Yagi. The VSWR is rather high at about 6-1 and I cannot risk blowing my new radio!

I have no way of taking down my pump up mast to adjust the matching on the antenna. The current restrictions mean I cannot get my fellow club members around to help me drop the mast.

As this means my activities on 432MHz have to be put on hold for possibly many more months I need to find an interim solution. In the mist and cobwebs of mind I recall an ATU for UHF frequencies. I did a quick search and nothing came up.

Can any group member confirm if an ATU for 432 MHz is practical and if so any reference to one?

Many thanks

Julian G4ZOD

_._,_._,_


Re: 432MHz ATU?

Mark GM4ISM
 

Julian

A 6:1 VSWR is about 3dB Return Loss. Think of it of this way, if your feeder has 1.5dB  loss (not unreasonable)

and you had no antenna at all, just an open cct, you would get 3dB Return Loss (feeder loss x 2)  I suspect that whatever is left of the connection to the yagi will not radiate that well... 

Whist matching that is theoretically possible, the  'good' match would likely  be very narrowband and  changing frequency may  make the mismatch worse, risking damage  anyway.

 If the mismatch changes in any way  the matching cct will make it worse,  risking damage.

 If you must use this  a 6dB power attenuator rated at the full TX power would add 12dB to the  return loss,  The rig will probably survive 15dB return loss 1.4:1 VSWR  That sort of attenuator is not common

You will hear and work even less but the rig would be reasonably safe

 Best option is to pop a dipole on a long fishing pole and use that as an antenna. It will probably work better than what is left of your MET

I do not recommend trying to use the MET antenna until it is fixed.

Mark GM4ISM



On 15/02/2021 23:03, g4zod@... via groups.io wrote:

I have a long term problem with my 17 element MET Yagi. The VSWR is rather high at about 6-1 and I cannot risk blowing my new radio!

I have no way of taking down my pump up mast to adjust the matching on the antenna. The current restrictions mean I cannot get my fellow club members around to help me drop the mast.

As this means my activities on 432MHz have to be put on hold for possibly many more months I need to find an interim solution. In the mist and cobwebs of mind I recall an ATU for UHF frequencies. I did a quick search and nothing came up.

Can any group member confirm if an ATU for 432 MHz is practical and if so any reference to one?

Many thanks

Julian G4ZOD


Virus-free. www.avg.com


Re: 432MHz ATU?

ian hope (2E0IJH)
 

Yes MFJ make one, MFJ-924, but looks hard to get, https://www.hamradio.co.uk/accessories-aerial-tuning-units-mfj-aerial-tuning-units/mfj/mfj-924-antenna-tuner-w-wattmeter-pd-44.php
 
Ian
M5IJH

 
 
Sent: Monday, February 15, 2021 at 11:03 PM
From: "g4zod@... via groups.io" <g4zod@...>
To: UKMicrowaves@groups.io
Subject: [UKMicrowaves] 432MHz ATU?

I have a long term problem with my 17 element MET Yagi. The VSWR is rather high at about 6-1 and I cannot risk blowing my new radio!

I have no way of taking down my pump up mast to adjust the matching on the antenna. The current restrictions mean I cannot get my fellow club members around to help me drop the mast.

As this means my activities on 432MHz have to be put on hold for possibly many more months I need to find an interim solution. In the mist and cobwebs of mind I recall an ATU for UHF frequencies. I did a quick search and nothing came up.

Can any group member confirm if an ATU for 432 MHz is practical and if so any reference to one?

Many thanks

Julian G4ZOD


432MHz ATU?

g4zod@btinternet.com
 

I have a long term problem with my 17 element MET Yagi. The VSWR is rather high at about 6-1 and I cannot risk blowing my new radio!

I have no way of taking down my pump up mast to adjust the matching on the antenna. The current restrictions mean I cannot get my fellow club members around to help me drop the mast.

As this means my activities on 432MHz have to be put on hold for possibly many more months I need to find an interim solution. In the mist and cobwebs of mind I recall an ATU for UHF frequencies. I did a quick search and nothing came up.

Can any group member confirm if an ATU for 432 MHz is practical and if so any reference to one?

Many thanks

Julian G4ZOD


Re: Programming Nort SLO registers

Daniel DL3IAE
 

Hi Noel,
I have just sent you an emails with some info.
Hope it helps.

73
Daniel


Re: Matching LDMOS device

Greg - ZL3IX
 

I'm not a PA specialist, but have designed one or two in the distant past. I believe that you need to use the impedance characteristics under drive at a typical power level, and these are not usually the same as would be the case under small signal conditions, ie when measured with a VNA. Making impedance measurements under drive is not a simple matter, and you may do well to take the manufacturer's data, here https://www.nxp.com/docs/en/data-sheet/MRF184.pdf.  Admittedly it only goes to 1 GHz, so you would need to attempt extrapolation up to 1.3 GHz. Even at 1 GHz the plot looks like around 1 ohm for Zin, which is way different from the 13 ohms you measured on your VNA.


Re: Programming Nort SLO registers

Noel G8GTZ
 

Hi Daniel,

Yes, I have done the hardware mods on one of my 2 units - Frequencies are 2916MHz for one unit for 432 IF and 3060 for the 2nd unit for 10,368 IF.

73
Noel - G8GTZ


Re: Matching LDMOS device

geoffrey pike
 

Hi Clive,
You dont say what the original device was in this case. The VNA reading is what not the old device as its broken? anyway the if its the old device its too high and the sign is probably wrong.
Anyway what to do, i recently did something at 2.4 GHz with a LDMOS device on a blank canvas Rogers 4003 i think
 I used an old DOS program called Puff from CalTech (there must be a modern equivalent)
So you obviously need to have some impedance info from the the data sheet and the substrate Er.
The process i use is to take the the complex input impedance and initially match it to the geometric mean of the source impedance and device impedance, in this case about 6 ohms, then match this to 50 ohms. So both the input and output are transformed in 2 stages and not directly from 0.7 ohms to 50 ohms or 1.6 ohms to 50 ohms.
The Puff program will give you the length of the low Z transmission line (try around 10 to 12 Ohms to give reasonable line dimensions) that you need to take the input or output to this level and real. Then transform to 50 ohms with another line.
All very vague but it will do it. Puff will take the complete s-parameter file and then you can try it over the F range you are interested in, at this point S12 will raise its head and the values you got for the input and output match need to be fine tuned with either flakes or strips previously etched onto the pcb. As S12 is 0.007 you may see only a small effect.
Puff runs under Windows XP but i haven't yet managed to get it to run under Windows 10.


Inline image


Inline image
These 2 quick look examles use a single low Z line to do the transformation and not 2 as mentioned previously, i used the data for 1GHz at 1,3GHz. Worth a try ! ( the output line was shortened to allow a trimmer to finish the transformation)
cheers
Geoff
GI0GDP

On Sunday, 14 February 2021, 21:49:42 GMT, Clive, G3GJA <clive@...> wrote:


Can someone explain how to approach matching an LDMOS PA transistor. I’m repairing a 23cm PA that used a PCB cut from a power amplifier designed around a device internally matched for use around 1485MHz. The PCB had been snowflaked on the output line and a trimmer added to the input matching to get the amp to work at 23cm.

 

The original device was overdriven resulting in the gate insulation breaking down. The replacement, an MRF184, is not ideal but should still be usable.

 

I can look at the input with my miniVNA and extract the input impedance at 23cm; it’s 13.3 -j42.4. Is this valid? Is there an easy way to use an online Smith Chart simulator to work out what I need to do to get the input to look like 50R?

 

I presume that the reading is not much help as it is what is presented to the input socket and not the device itself. The problem isn’t helped by not knowing exactly what frequency the amplifier was originally designed for, so I’ve no idea what the existing matching is doing.

 

Where do I start?

 

TIA

 

Clive G3GJA



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Registered in England No. 3003479. The information contained in this email may be legally privileged and/or confidential. If you are not the intended recipient, use of this information (including disclosure, copying or distribution) or any action taken, or omitted to be taken, in reliance on it is prohibited and may be unlawful; therefore please inform the sender and delete the message immediately. The views expressed in this email are those of the originator and not necessarily those held by HESH Computer Services Ltd, who do not accept liability for any action taken in reliance on the contents of this message or for the consequences of any computer viruses which may have been transmitted by this email.


Re: Programming Nort SLO registers

am.andrej@...
 

Hi,
 
If you decrease the frequency the output level will decrease too.
I soldered the PCB track before HMC and got more output power then.
 
73 de Andrej S57NML


Re: SPI Software

Mike Willis
 

SPI Driver Core is good for checking things. There is one for I2C as well.


--
Mike G0MJW


Re: Programming Nort SLO registers

Daniel DL3IAE
 

Hi Noel,

what is the frequency you try to program the 4153?
Are you getting a lock detect signal from it?
You should do the hardware mods I suggested at the bottom of the page.
It works nicely in my 24 GHz rig.

73
Daniel
DL3IAE


Programming Nort SLO registers

Noel G8GTZ
 

Hi

 

I’m trying to use a Nort SLO module https://wiki.microwavers.org.uk/Nort_SLO as the LO on 47GHz but having problems finding the correct register values to give low phase noise – the values on the wiki don’t seem to be optimum....

 

I’ve downloaded the AD Frac-N PLL calculator for the ADF4153 to generate values but the results I get compared to an Elcom and another Nort SLO programmed for 76GHz LO show the noise floor to be about 20 dB higher!

 

Has anyone programmed these devices, which were on sale at Friedrichshafen a couple of years ago, and can send me register values that you know work?

 

Thanks

Noel – G8GTZ


Re: SPI Software

Glyn M0XGT
 

On Sun, Feb 14, 2021 at 10:03 PM, G8ZHA wrote: 

I just want some software that will allow me to specify a number of bytes to be sent, then to allow me to load up the bytes and send them.

 An Arduino is probably the easiest for loading up some bytes and transferring them over SPI.

Cut and paste the code below into the Arduino IDE for a quick starting point - check the device datasheet for a sensible SPI bus speed and choose the SPIMode to match the SPI clock polarity and phase. The code transfers the bytes in buffer[] over SPI MOSI/MISO/CLK pins using Arduino pin 10 for SPI chip select and prints the sent and received data.  The screenshot is a capture of the data on the bus.

Glyn M0XGT

//---------------------------snip-------------------------
// Arduino SPI
#include <SPI.h>
#include <stdint.h>
 
// SPIMode CPOL CPHA
// ---------------
//   0      0    0
//   1      0    1
//   2      1    0
//   3      1    1
// ---------------
 
// SPI chip select pin
const int pin_cs = 10;
 
// SPI bus speed [Hz], bit-order, mode
SPISettings spi_settings(1000000, MSBFIRST, SPI_MODE3); 
 
// transfer bytes over SPI
void spi_transfer(uint8_t buffer[], int length, int pin_cs)
{
  digitalWrite(pin_cs, LOW);
  SPI.beginTransaction(spi_settings);
  SPI.transfer(buffer, length);
  SPI.endTransaction();
  digitalWrite(pin_cs, HIGH);
}
 
// print buffer
void print_buffer(String text, uint8_t buffer[], int n)
{
  Serial.print(text);
  Serial.print(":");
  for (int i = 0; i < n; i++) {
    Serial.print(' ');
    Serial.print(buffer[i], HEX);
  }
  Serial.print('\n');
}
 
void setup()
{
  // serial
  Serial.begin(19200);
  while (!Serial) {
    ; // wait for serial
  }
 
  // SPI
  SPI.begin();
  pinMode(pin_cs, OUTPUT);  // chip select pin
}
 
void loop()
{
  // fill a buffer with some bytes
  uint8_t buff[] = { 0x01, 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd, 0xef };
  int n = sizeof(buff) / sizeof(uint8_t);
 
  // print the buffer
  print_buffer("sending", buff, n);
 
  // transfer bytes
  spi_transfer(buff, n, pin_cs);
 
  // print what came back
  print_buffer("received", buff, n);
 
  delay(1000);  // [mS]
}
//---------------------------snip-------------------------


Re: SPI Software

Jim Mcilroy
 

Yes

My error.

Jim

On 15/02/2021 12:14, Andy G4JNT wrote:
40 bits actually.  32 for the frequency, and another 8 bits for control (which have to be correct)



On Mon, 15 Feb 2021 at 12:08, Jim Mcilroy via groups.io <gts53=btinternet.com@groups.io> wrote:


The AD9850 is set on frequency using a 32-bit word



Re: SPI Software

Andy G4JNT
 

40 bits actually.  32 for the frequency, and another 8 bits for control (which have to be correct)



On Mon, 15 Feb 2021 at 12:08, Jim Mcilroy via groups.io <gts53=btinternet.com@groups.io> wrote:


The AD9850 is set on frequency using a 32-bit word



Re: SPI Software

Jim Mcilroy
 

Hi

It may be worth searching for some AD9850 code. That has an SPI interface which is usually implemented using a 'bit banging' technique which is a hardware SPI (I think) rather than dedicated SPI pins.

The AD9850 is set on frequency using a 32-bit word

I probably have some Arduino code like that somewhere.

Jim  G4EQX

On 14/02/2021 22:12, Andy G4JNT wrote:
I had one like that once.   I gave it a dedicated PIC interface that read it as fast as possible and just chuck put what was needed on serial stop-start line in my chosen format.



On Sun, 14 Feb 2021 at 22:09, Robin Szemeti - G1YFG <robin@...> wrote:
Oh, and the small compass modules .. I assume you mean the 9 axis compass/gyro things?  I've played extensively with those on a project  .. they are a bit "tricky", you have to keep a hell of a rate up reading them,  if you don't read them often enough, they just lock up ... I had one running on an Arduino being read by SPI, and it was 100% fine ... until I added a few functions reading a GPS chip .. and it got upset when the micro spent too long messing arounf with GPS messages and woudl just hang the compass chip. it wasn't interrupt driven either, just a loop.


On Sun, 14 Feb 2021 at 22:05, Robin Szemeti <robin@...> wrote:
Plenty of Arduino stuff around, and you can program an Arduino with a simple USB cable ... that's the way I would go.

On Sun, 14 Feb 2021 at 22:03, G8ZHA via groups.io <g8zha-1=blueyonder.co.uk@groups.io> wrote:

AD also do a VHF/UHF version, somewhat cheaper.

 

I just want some software that will allow me to specify a number of bytes to be sent, then to allow me to load up the bytes and send them.

 

From: UKMicrowaves@groups.io [mailto:UKMicrowaves@groups.io] On Behalf Of Colin G4EML
Sent: 14 February 2021 21:32
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] SPI Software

 

An interesting chip, SPI is well supported by Arduinos or Pics so controlling it wouldn’t be a problem.  

 

However at £500 each I think I will give it a miss for a while!.

 

Colin G4EML

 

 

 

From: G8ZHA via groups.io
Sent: 14 February 2021 21:15
To: UKMicrowaves@groups.io
Subject: [UKMicrowaves] SPI Software

 

I wonder if anyone knows if there is any software about that can control a device connected via an SPI bus.

 

There are small compass modules available that are SPI controlled. Along with various PLL modules.

 

Also, Analog Devices has released a SPI controlled Filter chip ADMV8818 which maybe useful for amateur use.

 

 

 

Regards, Rich G8ZHA

 


--
Robin Szemeti - G1YFG


HP432A power meter disposal

g3zqu
 

Hi All,
I am having a thinning out of some of my test gear, getting rid of duplicates, and I have a nice HP432A for disposal.
It is complete with its sensor lead and a K486A thermister mount which covers 18 to 26.5GHz.
I also have a Marconi 6950, meter only for disposal as well.
Any interest please contact off list to callsign at btinternetdotcom
Martin G3ZQU


Re: Matching LDMOS device

Robin Szemeti - G1YFG
 

To stand a realistic chance of a predictive match using a Smith chart you really need all 4 S parameters.  I use SimSmith, as it makes things a bit easier ... but remember the input match "sees" a bit of the output match through S12 so  its not just a question of finding S22 and thats all you need, there is considerable interplay between the input and the output.

You do need the S parameters right at the device terminals though to produce a design from scratch,  VNA's with an S parameter test set come with sets of calibrations that allow you to calibrate and set the reference plane right up to the device terminals, compensating for all the cable lengths.

If you look on Page 7 of the datasheet, you'll find all the S parameters .. you could do worse than use SimSmith with an "S" block to represent the device ... you could simulate the exiting matching in SimSmith and then see what you need to add/take away to sort it out ...



On Sun, 14 Feb 2021 at 21:49, Clive, G3GJA <clive@...> wrote:

Can someone explain how to approach matching an LDMOS PA transistor. I’m repairing a 23cm PA that used a PCB cut from a power amplifier designed around a device internally matched for use around 1485MHz. The PCB had been snowflaked on the output line and a trimmer added to the input matching to get the amp to work at 23cm.

 

The original device was overdriven resulting in the gate insulation breaking down. The replacement, an MRF184, is not ideal but should still be usable.

 

I can look at the input with my miniVNA and extract the input impedance at 23cm; it’s 13.3 -j42.4. Is this valid? Is there an easy way to use an online Smith Chart simulator to work out what I need to do to get the input to look like 50R?

 

I presume that the reading is not much help as it is what is presented to the input socket and not the device itself. The problem isn’t helped by not knowing exactly what frequency the amplifier was originally designed for, so I’ve no idea what the existing matching is doing.

 

Where do I start?

 

TIA

 

Clive G3GJA



HESH Typographic Logo

HESH Computer Services

hesh.co.uk
01482 324936

8 Louis Pearlman Centre, Goulton Street, Hull, HU3 4DL

Registered in England No. 3003479. The information contained in this email may be legally privileged and/or confidential. If you are not the intended recipient, use of this information (including disclosure, copying or distribution) or any action taken, or omitted to be taken, in reliance on it is prohibited and may be unlawful; therefore please inform the sender and delete the message immediately. The views expressed in this email are those of the originator and not necessarily those held by HESH Computer Services Ltd, who do not accept liability for any action taken in reliance on the contents of this message or for the consequences of any computer viruses which may have been transmitted by this email.


--
Robin Szemeti - G1YFG


Re: SPI Software

Andy G4JNT
 

I had one like that once.   I gave it a dedicated PIC interface that read it as fast as possible and just chuck put what was needed on serial stop-start line in my chosen format.



On Sun, 14 Feb 2021 at 22:09, Robin Szemeti - G1YFG <robin@...> wrote:
Oh, and the small compass modules .. I assume you mean the 9 axis compass/gyro things?  I've played extensively with those on a project  .. they are a bit "tricky", you have to keep a hell of a rate up reading them,  if you don't read them often enough, they just lock up ... I had one running on an Arduino being read by SPI, and it was 100% fine ... until I added a few functions reading a GPS chip .. and it got upset when the micro spent too long messing arounf with GPS messages and woudl just hang the compass chip. it wasn't interrupt driven either, just a loop.


On Sun, 14 Feb 2021 at 22:05, Robin Szemeti <robin@...> wrote:
Plenty of Arduino stuff around, and you can program an Arduino with a simple USB cable ... that's the way I would go.

On Sun, 14 Feb 2021 at 22:03, G8ZHA via groups.io <g8zha-1=blueyonder.co.uk@groups.io> wrote:

AD also do a VHF/UHF version, somewhat cheaper.

 

I just want some software that will allow me to specify a number of bytes to be sent, then to allow me to load up the bytes and send them.

 

From: UKMicrowaves@groups.io [mailto:UKMicrowaves@groups.io] On Behalf Of Colin G4EML
Sent: 14 February 2021 21:32
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] SPI Software

 

An interesting chip, SPI is well supported by Arduinos or Pics so controlling it wouldn’t be a problem.  

 

However at £500 each I think I will give it a miss for a while!.

 

Colin G4EML

 

 

 

From: G8ZHA via groups.io
Sent: 14 February 2021 21:15
To: UKMicrowaves@groups.io
Subject: [UKMicrowaves] SPI Software

 

I wonder if anyone knows if there is any software about that can control a device connected via an SPI bus.

 

There are small compass modules available that are SPI controlled. Along with various PLL modules.

 

Also, Analog Devices has released a SPI controlled Filter chip ADMV8818 which maybe useful for amateur use.

 

 

 

Regards, Rich G8ZHA

 


--
Robin Szemeti - G1YFG


Re: SPI Software

Andy G4JNT
 

There are a lot of variables to SPI, it is not a properly defined protocol.   Does data change on the positive or negative clock edge;  is it LSB first or LSM first?   Does LE/CE have to be held active for the duration of the data transfer, or is it pulsed at the end?  Is the active edge low going or high going? 
For I/O devices, are there separate IP and OP wires, or is the D line tristate?
Every ine of these can be different
So you see there can be no standard chip or interface, every one has to be customised.   WHich is why a programmable device like a PIC or something else is aways used



On Sun, 14 Feb 2021 at 22:03, G8ZHA via groups.io <g8zha-1=blueyonder.co.uk@groups.io> wrote:

AD also do a VHF/UHF version, somewhat cheaper.

 

I just want some software that will allow me to specify a number of bytes to be sent, then to allow me to load up the bytes and send them.

 

From: UKMicrowaves@groups.io [mailto:UKMicrowaves@groups.io] On Behalf Of Colin G4EML
Sent: 14 February 2021 21:32
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] SPI Software

 

An interesting chip, SPI is well supported by Arduinos or Pics so controlling it wouldn’t be a problem.  

 

However at £500 each I think I will give it a miss for a while!.

 

Colin G4EML

 

 

 

From: G8ZHA via groups.io
Sent: 14 February 2021 21:15
To: UKMicrowaves@groups.io
Subject: [UKMicrowaves] SPI Software

 

I wonder if anyone knows if there is any software about that can control a device connected via an SPI bus.

 

There are small compass modules available that are SPI controlled. Along with various PLL modules.

 

Also, Analog Devices has released a SPI controlled Filter chip ADMV8818 which maybe useful for amateur use.

 

 

 

Regards, Rich G8ZHA

 

1961 - 1980 of 62988