Date   

Re: Norton Amplifiers

Neil Smith G4DBN
 

I seem to recall seeing the layout of a Minicircuits amp that used hybrids and paired amplifier chains.  One of the benefits siuggested was that if one leg of the amp died, the other would carry one at only 6dB down, as well as being very linear and robust with a high output IP3.  I thought it was the ZRL-700+ but can't find the notes about the internal circuit of that one, so I might be wrong. NF is 2dB at 70cm and the gain is very high, so not much benefit unless it is close to the masthead. It wasn't the TAMP-72LN+ drop-in module either. Perhaps I was dreaming.

Neil G4DBN


Re: Norton Amplifiers

 

On Wed, 19 May 2021 at 18:46, Chris Bartram G4DGU <chris@...> wrote:
My approach, FWIW, to the design of a second stage of a 'bomb-proof'
receiver at 432 or 1296MHz would be to use a group of more modern MMIC
devices such as the PGA-105 combined together with hybrids. Two groups
of two combined using 0degree hybrids and then combined into a push-pull
amplifier would give very good performance, but beware of mixer damage
if you have strong local signals!!

73

Chris G4DGU

I think we need an Eimac 4CX10,000A  as a mixer in contests, with a 4CX250B in the front end. This reminds me, I need to send you some data sheets. I had forgotten about that but will do it asap.

Dave


Norton Amplifiers

Chris Bartram G4DGU
 

Having, courtesy of Dom, seen information on the Norton feedback amplifier circuit, can I just make a couple of comments from rather a lot of direct experience of 'noiseless' feedback linearised amplifiers, and related circuitry, make a few observations and comments?

I'm not suggesting that the basic negative feedback topology doesn't work. It does, but really only in its original format at VHF. The problem is that both the active device and the feedback transformer, like most circuit elements at high frequencies, have phase shifts which can easily combine at frequencies above the operating frequency to produce positive feedback. If the gain of the amplifier is greater than unity at that frequency, a spurious oscillation WILL result! I have a tee-shirt collection ...

Those of us who were using the technique 40 years ago were able to make stable amplifiers using now historical devices like the BFT66, BFR91, BFR96 etc. They worked - with a bit of fiddling, such as a ferrite bead in series with the collector lead simply because the fT of the devices was quite small. I even managed to design a reliable NFB LNA using a C-band GaASFET at VHF, albeit using a different circuit. A lot of these designs found the way into production - indeed the FET amplifier circuit was ripped-off by another designer for an IF preamp design for a military radar!

The Ft of the next generation of bipolar devices was rather greater than that of the previous parts, and the simple Norton approach became untameable. Simply replacing the transistor in DJ7VY's design with something more recent is very likely indeed to result in an 'informal oscillator'!

There are other -ve feedback circuit topologies which can be used to make feedback linearised low-noise amplifiers (and interestingly transmitter power amplifiers) but they suffer from the need to have a hybrid in the input signal path. I have looked at linearising modern broad-band MMICs, but there isn't a simple reproducible topology which I've yet found despite a lot of playing both on the bench and by using modelling. I have achieved good performance from a couple of prototypes at 144, though, with IPI3 figures in the +30dBm region and NFs ~1.2dB, but they haven't proved reproducible.

My approach, FWIW, to the design of a second stage of a 'bomb-proof' receiver at 432 or 1296MHz would be to use a group of more modern MMIC devices such as the PGA-105 combined together with hybrids. Two groups of two combined using 0degree hybrids and then combined into a push-pull amplifier would give very good performance, but beware of mixer damage if you have strong local signals!!

73

Chris

G4DGU


Re: How does this POTY antenna work??

John Fell
 

Chris,
The pic shows a circular patch feed for 2.4GHz , similar to the POTY type .The N elbow feeds 2.4GHz RF to the patch element .
His site says he uses a 20W PA , so depending on the attenuation along the TX cable , he should put in a reasonable signal .

My system outputs 1.5W via a 5m run of LDF450 Heliax via an 80cm offset - that puts my signal at -5dB relative to the Beacons on QO100.

The SMA lead will connect a probe inside the round waveguide to the downconverter behind the assembly. An LNB is a downconverter , in this case a block + antenna .The N elbow plug will carry downconverted RF and DC to the shack end unit that will supply the required output RF for the radio in use.

What is interesting to see is the conical horn and rear choke flange (?) . I would be interested to know what interactions /pattern distortion occur on 2.4GHz .
Certainly the feed will be more efficient than open ended waveguide at 10GHz .

73
John
G0API

On Wed, 19 May 2021 at 10:32, Chris Wilson <chris@...> wrote:


  19/05/2021 10:19

I am slowly getting into amateur satellite work and runa 1.8 meter prime focus dish with a POTY antenna for 2.4GHz TX and a coaxial LNB for circa 10.5GHz reception. I know the LNB down converts to around 940 MHz using an intermediate frequency.

I heard a very nice signal from a chap who appeared to know a lot about the hardware used, so looked him up on qrz.com  He was using a POTY antenna the like of which I have not seen before. It has a feed horn and appears to feed the RX side without an LNB directly to a Kuhne down converter. How might that work, I thought down converters expected a lot of gain from the LNB and an already down converted signal, to some extent, done within the LNB?


I placed a photo of this nicely looking engineered device here:

http://www.chriswilson.tv/DJ8EI.JPG

It appears there's no LNB but the RX antenna is inside the POTY tube itself.


Thanks for any insight to this newbie!

--
       Best Regards,
                   Chris Wilson.
mailto: chris@...







Re: 6cm lo?

Gareth G4XAT
 

I have down-converted 5.66 DATV to 3.4 and fed it into a Titanium LNB  via a 1/4 wave probe (C1WPLL 3.4-4.2GHz) which mixes again down to 950-1750.
With some pipe caps to clean up the LO (2260 from a DDS) and the desired mixer output (3.4). Very pleased with how its working on the bench. BATC Ryde for DATV and Langstone for NB. 
Gareth


Re: 6cm lo?

militaryoperator
 

-----Original Message-----
From: geoffrey pike via groups.io <gi0gdp@...>
To: UKMicrowaves@groups.io <UKMicrowaves@groups.io>
Sent: Tue, 18 May 2021 17:40
Subject: Re: [UKMicrowaves] 6cm lo?

Try here


Thanks Geoff, 

5760 Lo on its way. Have also bought some W1GHZ boards for some 23cm preamps along with PGA103 devices.

Fun fun fun ahead!!!!!!

Ben.


Re: Farnell Handling Charge

Michael Scott
 

Sorry Mark, we have a few MAX ICs but not that one!

The whole catalogue is on the UKuG website, folow the links to the Chipbank.

73, Mike

On 19/05/2021 03:59, Mark M5BOP via groups.io wrote:
You don’t happen to have a supply of MAX4450EXK+T 210MHz op amps, SC-70-5 in the chipbank do you Mike?  If so, I’ll take ten! That would save me an order to Farnell or similar (with associated low-volume order costs!) - not building a 10MHz ref DA or anything!!

Thanks,
Mark M5BOP

Farnell Handling Charge 
From: Michael Scott
Date: Mon, 17 May 2021 16:31:27 BST 

Have to use the Chipbank instead!!

Mike.


3c. 
Re: Farnell Handling Charge 
From: Andy G4JNT
Date: Mon, 17 May 2021 16:35:02 BST 
I only wanted a handful of TS912 opamps.


Re: How does this POTY antenna work??

Colin G4EML
 

The Kuhne down converter does exactly the same job as a regular LNB. It just has a coax input instead of having an integral antenna. That arrangement simply connects an external antenna to it.

It is not really correct to call that a POTY antenna. The POTY is the name of a specific design, not a generic term.

Colin G4EML

On 19 May 2021, at 10:32, Chris Wilson <chris@chriswilson.tv> wrote:



19/05/2021 10:19

I am slowly getting into amateur satellite work and runa 1.8 meter prime focus dish with a POTY antenna for 2.4GHz TX and a coaxial LNB for circa 10.5GHz reception. I know the LNB down converts to around 940 MHz using an intermediate frequency.

I heard a very nice signal from a chap who appeared to know a lot about the hardware used, so looked him up on qrz.com He was using a POTY antenna the like of which I have not seen before. It has a feed horn and appears to feed the RX side without an LNB directly to a Kuhne down converter. How might that work, I thought down converters expected a lot of gain from the LNB and an already down converted signal, to some extent, done within the LNB?


I placed a photo of this nicely looking engineered device here:

http://www.chriswilson.tv/DJ8EI.JPG

It appears there's no LNB but the RX antenna is inside the POTY tube itself.


Thanks for any insight to this newbie!

--
Best Regards,
Chris Wilson.
mailto: chris@chriswilson.tv


How does this POTY antenna work??

Chris Wilson
 

19/05/2021 10:19

I am slowly getting into amateur satellite work and runa 1.8 meter prime focus dish with a POTY antenna for 2.4GHz TX and a coaxial LNB for circa 10.5GHz reception. I know the LNB down converts to around 940 MHz using an intermediate frequency.

I heard a very nice signal from a chap who appeared to know a lot about the hardware used, so looked him up on qrz.com He was using a POTY antenna the like of which I have not seen before. It has a feed horn and appears to feed the RX side without an LNB directly to a Kuhne down converter. How might that work, I thought down converters expected a lot of gain from the LNB and an already down converted signal, to some extent, done within the LNB?


I placed a photo of this nicely looking engineered device here:

http://www.chriswilson.tv/DJ8EI.JPG

It appears there's no LNB but the RX antenna is inside the POTY tube itself.


Thanks for any insight to this newbie!

--
Best Regards,
Chris Wilson.
mailto: chris@chriswilson.tv


G4bao 23and 70cm driver boards

John Worsnop
 

Bad news, RS have again pushed out the delivery date for the LDMOS device. Now it's the 6th of September. 

Might be time repurpose all the kit pcbs I have left! Sadly no suitable device in the same package. 
I wonder if anyone's suffering delays on the SG lab 23cm transverters as I think it uses the same device?

73

John


Re: Farnell Handling Charge

Mark M5BOP
 

You don’t happen to have a supply of MAX4450EXK+T 210MHz op amps, SC-70-5 in the chipbank do you Mike?  If so, I’ll take ten! That would save me an order to Farnell or similar (with associated low-volume order costs!) - not building a 10MHz ref DA or anything!!

Thanks,
Mark M5BOP

Farnell Handling Charge 
From: Michael Scott
Date: Mon, 17 May 2021 16:31:27 BST 

Have to use the Chipbank instead!!

Mike.


3c. 
Re: Farnell Handling Charge 
From: Andy G4JNT
Date: Mon, 17 May 2021 16:35:02 BST 

I only wanted a handful of TS912 opamps.


Re: [RSGB-Workshop] Farnell Handling Charge

 

On Mon, 17 May 2021 at 13:42, Andy G4JNT <andy.g4jnt@...> wrote:
Farnell have just, (as of today I was told) introduced a £2 handling charge on orders less than £40 for account holders.

So that's blown their credibility.   


It don't make much difference to me, as I usually place much larger orders. But there are companies with much larger minimum orders. Flann Microwave had a minimum order of £200 several years ago.  I wanted to order some plastic caps from a Caplugs distributor. The minimum order of them was quite significant. When I said this, the guy likened it to going into Tesco and wanting two teaspoons of sugar, and not being willing to buy a packet of sugar. He seemed to be overlooking that a packet of sugar is £1 or so, but the minimum order was £50 or so for each type. .When it became clear there was a long lead-time too, I ordered directly from the USA.

As far as I know, RS has no minimum order value.

Dave


Re: Farnell Handling Charge was zero

ian hope (2E0IJH)
 

I've got 2 accounts my radio one and Company one, radio one has handling charge, log in with company one and no charges
 
very weird
 
Ian
M5IJH

 
 
Sent: Tuesday, May 18, 2021 at 5:37 PM
From: "Andy G4JNT" <andy.g4jnt@...>
To: "UK Microwaves groups.io" <UKMicrowaves@groups.io>
Subject: Re: [UKMicrowaves] Farnell Handling Charge was zero
Madder and madder
Just tried again, £15 test order and it's back - all cancelled of course.
 
But is later in the day - wonder if that's got anything to do with it?
 
Andy
 
 
On Tue, 18 May 2021 at 17:20, Dave G8KHU <david@...> wrote:
I just tried a test order and the handling charge remained, I went right up to the submit page and it remained but the payment method was definitely set to trade account.

Wierd that different people have different experiences, I shall have a nag at customer service tomorrow.

Dave

 

 


Re: Farnell Handling Charge was zero

Andy G4JNT
 

It makes sure they keep customers and they're happy.   If you can get a product costing £1 with a few mouse clicks, then next time you want to spend £400 on components, the same few mouse clicks are only too easy to just do.



On Tue, 18 May 2021 at 17:40, Colin G4EML <colin@...> wrote:

There is something strange going on, the Farnell website delivery information page changes depending on if I am logged in or not. The free delivery line appears and disappears from the Trade accounts. It looks like they are probably in the middle of implementing a change. Maybe some accounts have the charge and some do not. Or maybe they have multiple servers and the web pages are different.

 

£2 handling charge is not actually too bad though. Non account customers get charged up to £9.95.

 

RS is still free for account holders but I can’t see that lasting much longer. Parcelforce next day delivery on a £1.00 order doesn’t make much commercial sense however convenient it is.

 

Colin.

 

 

 

 

From: Dave G8KHU
Sent: 18 May 2021 17:16
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Farnell Handling Charge was zero

 

I just tried a test order and the handling charge remained, I went right up to the submit page and it remained but the payment method was definitely set to trade account.

Wierd that different people have different experiences, I shall have a nag at customer service tomorrow.

Dave

 


Re: 6cm lo?

g4cch_1
 

Sub harmonic mixer, so use LO/2


Nissei MS-1228

geoffrey pike
 

Been working on this smpsu and i have found an obliterated zener on theTL494 control pcb, does anyone have one and can measure 
the voltage on the zener 
cheers
Geoff
GI0GDP
I think its 36v

Virus-free. www.avg.com


Re: 6cm lo?

geoffrey pike
 

On Tuesday, 18 May 2021, 17:14:04 BST, militaryoperator via groups.io <military1944@...> wrote:


Thinking on the LO for 5760, 4469 for 23cm if or 5328 for 70cm if.

The ADF4351 only goes to 4.4Ghz

The ADF4355 and MAX2870 goes to 6Ghx but the built boards on ebay are costly.

I tried the Bodnar unit, 810Mhz max so at 744 and using the harmonics, too low, needs amp. 

I guess I could use the 4351 at f/3 at 1488 for 23cm if or 1776 for 70cms, with a bit of amp/filtering?

I just wondered how others have supplied their LO freq?

Ben.

Virus-free. www.avg.com


Re: Farnell Handling Charge was zero

Colin G4EML
 

There is something strange going on, the Farnell website delivery information page changes depending on if I am logged in or not. The free delivery line appears and disappears from the Trade accounts. It looks like they are probably in the middle of implementing a change. Maybe some accounts have the charge and some do not. Or maybe they have multiple servers and the web pages are different.

 

£2 handling charge is not actually too bad though. Non account customers get charged up to £9.95.

 

RS is still free for account holders but I can’t see that lasting much longer. Parcelforce next day delivery on a £1.00 order doesn’t make much commercial sense however convenient it is.

 

Colin.

 

 

 

 

From: Dave G8KHU
Sent: 18 May 2021 17:16
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Farnell Handling Charge was zero

 

I just tried a test order and the handling charge remained, I went right up to the submit page and it remained but the payment method was definitely set to trade account.

Wierd that different people have different experiences, I shall have a nag at customer service tomorrow.

Dave

 


Re: Farnell Handling Charge was zero

Andy G4JNT
 

Madder and madder
Just tried again, £15 test order and it's back - all cancelled of course.

But is later in the day - wonder if that's got anything to do with it?



On Tue, 18 May 2021 at 17:20, Dave G8KHU <david@...> wrote:
I just tried a test order and the handling charge remained, I went right up to the submit page and it remained but the payment method was definitely set to trade account.

Wierd that different people have different experiences, I shall have a nag at customer service tomorrow.

Dave


Re: 6cm lo?

Andy G4JNT
 

(No. No PCBs available)



On Tue, 18 May 2021 at 17:14, militaryoperator via groups.io <Military1944=aol.com@groups.io> wrote:
Thinking on the LO for 5760, 4469 for 23cm if or 5328 for 70cm if.

The ADF4351 only goes to 4.4Ghz

The ADF4355 and MAX2870 goes to 6Ghx but the built boards on ebay are costly.

I tried the Bodnar unit, 810Mhz max so at 744 and using the harmonics, too low, needs amp. 

I guess I could use the 4351 at f/3 at 1488 for 23cm if or 1776 for 70cms, with a bit of amp/filtering?

I just wondered how others have supplied their LO freq?

Ben.

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