Measuring RF output impedance

[John Fields]

On Sun, 02 May 2004 09:04:33 -0500, John Fields
<jfields@austininstruments.com> wrote:

On Sun, 02 May 2004 14:09:44 +0100, Paul Burridge
pb@notthisbit.osiris1.co.uk> wrote:

On Sat, 1 May 2004 15:30:18 -0400, "Ralph Mowery" <rmowery@ctc.net
wrote:

The generators are more of a voltage source. They will deliver their rated
output when loaded to the proper impedance. Load it with 50 ohms and see if
it gives the rated output. If not try 70 ohms, or another value. One of
the reasons for using a 6 db pad is that it helps isolate the impedance of
the generator and receiver.

My main sig gen states "output EMF using 6dB pad" next to the socket.
WTF is a "6dB pad"?

---
A 6dB attenuator.

---
Also, less commonly, a device used to match the impedance of a
generator to the impedance of a transmission line or a load, or the
impedance of a transmission line to the impedance of a load.

The impedance of the generator, line, and/or load are assumed to be
purely resistive, and there is always loss associated with the
transformation. Devices which exhibit the least loss are called
"minimum loss pads", and

http://www.maxim-ic.com/appnotes.cfm/appnote_number/972

gives a good description of the process involved in designing one.

The reference given to Bruno Weinschel and the ITT handbook (as we
old-timers call it) is particularly good, and if you're interested in
RF (or just about anything else...) and you can buy a copy of it you
should.

BTW, since a pad is usually rated in terms of the power it's supposed
to lose between its input and its output, the reference to "output
EMF" on your generator may be what it supposed to be with a 3dB pad on
its output.

Easy way to find out would be to build a 3dB and a 6dB pad to find
out. For a 50 ohm tee pad, here are the resistor values you'll need
for -3dB:

0dBIN>--[8.55]-+-[8.55]-->-3dBOUT
|
[141.93]
|
GND>-----------+----------->GND


and for -6dB:

0dBIN>--[16.61]-+-[16.61]-->-3dBOUT
|
[66.93]
|
GND>------------+----------->GND

The input goes directly to your generator, (assuming its output
impedance is 50+j0 ohms) a 50 ohm resistor gets connected across the
output of the pad, and you'll measure the voltage across the 50 ohm
resistor.

Use non-inductive resistors (carbon comp if you can get them) and keep
the leads short. That is, ********KEEP THE LEADS SHORT*********.

--
John Fields

 

[John Jardine]

Paul Burridge <pb@notthisbit.osiris1.co.uk> wrote in message
news:mk87909cpdg7dq25dn24blfoph41mr2gpm@4ax.com...

Hi,

I have a spare RF signal generator that has an unmarked output from a
type of socket I've never seen before. What's the simplest way of
establishing its output impedance? I've had a few ideas but no doubt
someone out there will know of something better, since I always seem
to end up making unnecessary work for myself.
Any suggestions?

p.
--

The BBC: licenced at public expense to spread lies.

Those ex-military AVO's were really nice g.p. signal generators though could
never afford one. Seem to remember they were 50ohms out. The o/p socket and
plug were standard 50's military chic and still available.
regards
john

 

[John Crighton]

On Sun, 02 May 2004 14:08:38 +0100, Paul Burridge
<pb@notthisbit.osiris1.co.uk> wrote:

On Sun, 02 May 2004 02:43:18 GMT, john_c@tpg.com.au (John Crighton)
wrote:


Hello Paul,
what is the brand name and model number of your RF signal generator.
Can you descibe the socket to us.

Thanks John (and others).

The model number ain't gonna mean a lot to anyone as this is a very
old piece of kit (1950s) that I keep mainly out of a sense of
reverence for the past. It's an old ex-RAF AVO. I have posted a
picture of the socket to a.b.s.e under this same thread title...
BTW, there's a 5p coin shown for scale, but since that won't mean much
to anyone outside Britain, the outer of the socket is approx. 1" in
diameter (which won't mean much to anyone in europe but it serves them
right for adopting the metric system.)

--

The BBC: licenced at public expense to spread lies.

Go on, tell us the model number, there are a lot of us
still interested in boat anchor style test equipment.

Is this unit similar to your sig gen
http://www.thevalvepage.com/testeq/avo/sg3/sg3.htm
http://www.thevalvepage.com/testeq/testeq.htm
Unfotunately the connector has been removed and a
BNC type fitted.

I am guessing that you want to keep the original connector
on the sig gen and find a matching connector to make a
short test lead. Old Style connector to BNC.
My news group service doesn't allow me to see the group
a.b.s.e Pity. So I can not see the picture you posted.

So, what are the results of connecting your ohm meter
to the RF out put connector (with the unit switched off)
and measuring the resistance on all attenuator positions.

On one of the lower frequency ranges when you connect
up your cro via a "T" piece to the sig gen with say a 75
ohm load. Does the output level jump up to double
when the load is removed?

Repeat the experiment with a 50 ohm load. If the voltage
doubles from loaded to no load, you will be laughing.
But I don't think you will be that lucky.

I am guessing it will be closer to 75 ohm output impedance.

Try different value loads and let us know how you got on.

Cheerio,
John Crighton
Sydney

 

[Active8]

On Sun, 02 May 2004 11:35:08 -0500, John Fields wrote:

On Sun, 02 May 2004 09:04:33 -0500, John Fields
jfields@austininstruments.com> wrote:

snip John helping Paul with terminology

http://www.maxim-ic.com/appnotes.cfm/appnote_number/972

Once in a while, I can post a helpful link (I've got plenty of tech
info links, but most don't usually apply to the topic at hand
whatever that may be) , but some of you guys, like Spehro, You,
etc., ... it's like you can pull horshoe out of yer asses You
must do more digging than I do.

I got a kick out of this link because I have the opposite situation.
I don't need an MLP becuse I have an SLM tha *is* 75 ohfriggin'megas
and the link dealt with ... you know.

snip John still helping but going the extra furlong or so

Use non-inductive resistors (carbon comp if you can get them) and keep
the leads short. That is, ********KEEP THE LEADS SHORT*********.
^^^^^^^^^^

advice that should be unsnipped. Er, snip the leads, though.

--
Best Regards,
Mike

 

[Paul Burridge]

On Sun, 02 May 2004 22:37:28 GMT, john_c@tpg.com.au (John Crighton)
wrote:

Go on, tell us the model number, there are a lot of us
still interested in boat anchor style test equipment.

Is this unit similar to your sig gen
http://www.thevalvepage.com/testeq/avo/sg3/sg3.htm
http://www.thevalvepage.com/testeq/testeq.htm
Unfotunately the connector has been removed and a
BNC type fitted.

Not really similar to any of them, I'm afraid. Model number is CT
378B. I did recognise that old Advance E2, though. Had one of 'em
about 25 years ago. It was pretty ancient then!

I am guessing that you want to keep the original connector
on the sig gen and find a matching connector to make a
short test lead. Old Style connector to BNC.
My news group service doesn't allow me to see the group
a.b.s.e Pity. So I can not see the picture you posted.

Pity. Hopefully some kind soul will post it onto a web site for you. I
can't as I have no FTP s/ware installed at present. :-(
The output is just under an inch in diameter and is co-axial as you
might expect. The centre pin is about 1/16th" thick and doesn't
protrude beyond the outer. It's pretty unremarkable apart from its
size; much larger than one usually sees.
--

The BBC: licenced at public expense to spread lies.

 

[Paul Burridge]

On Mon, 3 May 2004 02:28:46 -0400, Active8 <reply2group@ndbbm.net>
wrote:

On Sun, 02 May 2004 11:35:08 -0500, John Fields wrote:

On Sun, 02 May 2004 09:04:33 -0500, John Fields
jfields@austininstruments.com> wrote:

snip John helping Paul with terminology

http://www.maxim-ic.com/appnotes.cfm/appnote_number/972

Once in a while, I can post a helpful link (I've got plenty of tech
info links, but most don't usually apply to the topic at hand
whatever that may be) , but some of you guys, like Spehro, You,
etc., ... it's like you can pull horshoe out of yer asses You
must do more digging than I do.

Yup, John Chrighton's another one that springs to mind as being very
good at sniffing stuff out on the Web.

I'd often wondered what these "pads" were for. I'd been a bit
concerned to note that the output amplitude varied quite markedly when
sweeping the generator through it's frequency range when measuring the
'open circuit' voltage with a 'scope. I guess now I know why.
Thanks, guys.
--

The BBC: licenced at public expense to spread lies.

 

[John Fields]

On Mon, 03 May 2004 12:56:07 +0100, Paul Burridge
<pb@notthisbit.osiris1.co.uk> wrote:

On Sun, 02 May 2004 22:37:28 GMT, john_c@tpg.com.au (John Crighton)
wrote:

Go on, tell us the model number, there are a lot of us
still interested in boat anchor style test equipment.

Is this unit similar to your sig gen
http://www.thevalvepage.com/testeq/avo/sg3/sg3.htm
http://www.thevalvepage.com/testeq/testeq.htm
Unfotunately the connector has been removed and a
BNC type fitted.

Not really similar to any of them, I'm afraid. Model number is CT
378B. I did recognise that old Advance E2, though. Had one of 'em
about 25 years ago. It was pretty ancient then!

I am guessing that you want to keep the original connector
on the sig gen and find a matching connector to make a
short test lead. Old Style connector to BNC.
My news group service doesn't allow me to see the group
a.b.s.e Pity. So I can not see the picture you posted.

Pity. Hopefully some kind soul will post it onto a web site for you. I
can't as I have no FTP s/ware installed at present.

---
Can't you just email it to him?

--
John Fields

 

[Steve Nosko]

"Ralph Mowery" <rmowery@ctc.net> wrote in message
news:l9CdnXjL-OuzmQjdRVn-jw@ctc.net...

My main sig gen states "output EMF using 6dB pad" next to the socket.
WTF is a "6dB pad"?
--

[...snip...]
For the calibration to be accurate on your generator it sounds like the
scale is calibrated so you need the 6 db pad after it. A 5 db pad will
reduce the power by a factor of 4 or a voltage by a factor of 2.

That last 5 should be a 6.

--
Steve N, K,9;d, c. i My email has no u's.>
>

 

[Steve Nosko]

"Paul Burridge" <pb@notthisbit.osiris1.co.uk> wrote in message
news:mk87909cpdg7dq25dn24blfoph41mr2gpm@4ax.com...

Hi,

I have a spare RF signal generator that has an unmarked output from a
type of socket I've never seen before. What's the simplest way of
establishing its output impedance? I've had a few ideas but no doubt
someone out there will know of something better, since I always seem
to end up making unnecessary work for myself.
Any suggestions?
p.
--
The BBC: licenced at public expense to spread lies.

One more thing to keep in mind, Paul. Over here in the US it is and has for
a long time been standard to display the LOAD level on the generator output
indicator. That is, the voltage (or power) at the load itself (assuming
matched). In the UK - but I don't know about recently, it was common to
show the generator EMF -- which meant the internal generator voltage. This
would be twice what would appear across the load if the load & source Z were
equal.

From your Sig you may very well be familiar with the EMF designation...
--
Steve N, K,9;d, c. i My email has no u's.

 

[Paul Burridge]

On Mon, 03 May 2004 10:44:14 -0500, John Fields
<jfields@austininstruments.com> wrote:

On Mon, 03 May 2004 12:56:07 +0100, Paul Burridge
pb@notthisbit.osiris1.co.uk> wrote:

On Sun, 02 May 2004 22:37:28 GMT, john_c@tpg.com.au (John Crighton)
wrote:

Go on, tell us the model number, there are a lot of us
still interested in boat anchor style test equipment.

Is this unit similar to your sig gen
http://www.thevalvepage.com/testeq/avo/sg3/sg3.htm
http://www.thevalvepage.com/testeq/testeq.htm
Unfotunately the connector has been removed and a
BNC type fitted.

Not really similar to any of them, I'm afraid. Model number is CT
378B. I did recognise that old Advance E2, though. Had one of 'em
about 25 years ago. It was pretty ancient then!

I am guessing that you want to keep the original connector
on the sig gen and find a matching connector to make a
short test lead. Old Style connector to BNC.
My news group service doesn't allow me to see the group
a.b.s.e Pity. So I can not see the picture you posted.

Pity. Hopefully some kind soul will post it onto a web site for you. I
can't as I have no FTP s/ware installed at present.

---
Can't you just email it to him?

Oh yeah. I forgot about that!
Better ask here first though, as it's a binary and might not be
welcome.
I've also taken a shot of the whole gen., John. I can certainly e-mail
the pics to you if you're that interested in boat anchors (although
this one's only 25lbs so hardly qualifies). My Marconi, OTOH, has got
to be 3 times that much at least...

--

The BBC: licenced at public expense to spread lies.

 

[John Crighton]

On Mon, 03 May 2004 18:59:30 +0100, Paul Burridge
<pb@notthisbit.osiris1.co.uk> wrote:

Can't you just email it to him?

Oh yeah. I forgot about that!
Better ask here first though, as it's a binary and might not be
welcome.
I've also taken a shot of the whole gen., John. I can certainly e-mail
the pics to you if you're that interested in boat anchors (although
this one's only 25lbs so hardly qualifies). My Marconi, OTOH, has got
to be 3 times that much at least...

--

The BBC: licenced at public expense to spread lies.

Hello Paul,
Yes, I would be interested to see the pictures of the AVO CT378B
What was the Marconi sig gen model number? I missed it.
No need for pictures of the Marconi unit. I might know it from
the model number.
Regards,
John Crighton
Sydney

 

[Highland Ham]

The model number ain't gonna mean a lot to anyone as this is a very
old piece of kit (1950s) that I keep mainly out of a sense of
reverence for the past. It's an old ex-RAF AVO. I have posted a
picture of the socket to a.b.s.e under this same thread title...
BTW, there's a 5p coin shown for scale, but since that won't mean much
to anyone outside Britain, the outer of the socket is approx. 1" in
diameter (which won't mean much to anyone in europe but it serves them
right for adopting the metric system.)
======================

Since Britain is part of Europe you probably mean 'anyone in continental
europe'

Just for your info ,the metric system was introduced /imposed by Napoleon
(eg more than 200 years ago)
For once he did the right thing .

Frank GM0CSZ / KN6WH

 

[Paul Burridge]

On Mon, 03 May 2004 22:14:15 GMT, john_c@tpg.com.au (John Crighton)
wrote:

Hello Paul,
Yes, I would be interested to see the pictures of the AVO CT378B
What was the Marconi sig gen model number? I missed it.
No need for pictures of the Marconi unit. I might know it from
the model number.

Okay, John. The Marconi's a TF 2002AS. I'll post you a pic of the AVO
2morrow as I'm a bit shagged-out right now (bank holiday boozing here
2day).
--

The BBC: licenced at public expense to spread lies.

 

[Tim Auton]

"Highland Ham" <xygm0csz.wvkn6wh@ntlworld.com> wrote:

The model number ain't gonna mean a lot to anyone as this is a very
old piece of kit (1950s) that I keep mainly out of a sense of
reverence for the past. It's an old ex-RAF AVO. I have posted a
picture of the socket to a.b.s.e under this same thread title...
BTW, there's a 5p coin shown for scale, but since that won't mean much
to anyone outside Britain, the outer of the socket is approx. 1" in
diameter (which won't mean much to anyone in europe but it serves them
right for adopting the metric system.)
======================
Since Britain is part of Europe you probably mean 'anyone in continental
europe'

Just for your info ,the metric system was introduced /imposed by Napoleon
(eg more than 200 years ago)
For once he did the right thing .

The metric system also the law here in the UK. You can't sell stuff in
pounds and ounces or feet and inches. Miles are the last bastion of
the imperial system (on road signs), with the informal exception of
pints of beer (IIRC technically it's a "large" beer and 576ml). I
don't mind working in metric units, indeed I prefer them, but if
anyone wants to stop me asking for a pint in the pub they'll have a
fight on their hands!

Oh yes, cannabis is still sold by the fraction of an ounce as it ever
was, but I don't think selling cannabis in imperial units is any more
illegal than just selling cannabis


Tim
--
Love is a travelator.

 

[Ralph Mowery]

[...snip...]
For the calibration to be accurate on your generator it sounds like the
scale is calibrated so you need the 6 db pad after it. A 5 db pad will
reduce the power by a factor of 4 or a voltage by a factor of 2.

That last 5 should be a 6.

--
Steve N, K,9;d, c. i My email has no u's.

Thanks, I fat fingered that and hit the 5 instead of the 6.

 

[John Crighton]

On Tue, 04 May 2004 00:21:38 +0100, Paul Burridge
<pb@notthisbit.osiris1.co.uk> wrote:

On Mon, 03 May 2004 22:14:15 GMT, john_c@tpg.com.au (John Crighton)
wrote:

Hello Paul,
Yes, I would be interested to see the pictures of the AVO CT378B
What was the Marconi sig gen model number? I missed it.
No need for pictures of the Marconi unit. I might know it from
the model number.

Okay, John. The Marconi's a TF 2002AS. I'll post you a pic of the AVO
2morrow as I'm a bit shagged-out right now (bank holiday boozing here
2day).
--

The BBC: licenced at public expense to spread lies.

Yes, I know that unit, I have a 2001
Repairing that unit is not dead easy for hobbyists.

I am assuming that AVO at Dover were useless with your
enquiries regarding information on the AVO CT378B

If you wanted a good back up signal generator,
that is dead easy to repair. Here is one for sale.
Marconi TF 144H 50 ohms output Z. BNC connector.
10KHz to 72MHz
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&category=40004&item=3094746090&rd=1

I like that model, for a number of reasons.
Very stable frequency wise (when warmed up).
It has that nice smell inside that you get from valve gear. LOL
Everything inside is getatable.
Big knobs and easy to read dials, good for failing eyesight.
When the attenuator gets smoked by accidentally pressing a
microphone push to talk button of a transceiver under repair
on the bench, it is very easy to replace the resistors in the
attenuator.
It was not that heavy that I couldn't hump it up the gangways
of ships, decades ago, to do radio service work but it is way too
heavy for me now. Heh heh heh...

You might like to check out how far away that unit for auction,
is away from you. I wouldn't pay any more than 45 quid.
Even 25 quid is right on the limit for me. But if no one bids
you could get lucky. I bought one here in Australia for $10
at a Ham fest.

I only mentioned the TF144H incase you were looking for a
good cheap sig gen to accompany your TF2002AS do some
serious radio receiver work. Both have good attenuators.
Having two good signal generators would help you out with
all that filter and interference work that has been plaguing you
over recent months. One sig gen as the desired signal, the
second sig-gen as the interfering signal etc.

Regards,
John Crighton
Sydney

 

[Terry Given]

"Tim Auton" <tim.auton@uton.[groupSexWithoutTheY]> wrote in message
news:l8md90h7liefj5fr0cq187v482gk3b5hm6@4ax.com...

"Highland Ham" <xygm0csz.wvkn6wh@ntlworld.com> wrote:

The model number ain't gonna mean a lot to anyone as this is a very
old piece of kit (1950s) that I keep mainly out of a sense of
reverence for the past. It's an old ex-RAF AVO. I have posted a
picture of the socket to a.b.s.e under this same thread title...
BTW, there's a 5p coin shown for scale, but since that won't mean much
to anyone outside Britain, the outer of the socket is approx. 1" in
diameter (which won't mean much to anyone in europe but it serves them
right for adopting the metric system.)
======================
Since Britain is part of Europe you probably mean 'anyone in continental
europe'

Just for your info ,the metric system was introduced /imposed by Napoleon
(eg more than 200 years ago)
For once he did the right thing .

The metric system also the law here in the UK. You can't sell stuff in
pounds and ounces or feet and inches. Miles are the last bastion of
the imperial system (on road signs), with the informal exception of
pints of beer (IIRC technically it's a "large" beer and 576ml). I
don't mind working in metric units, indeed I prefer them, but if
anyone wants to stop me asking for a pint in the pub they'll have a
fight on their hands!

Oh yes, cannabis is still sold by the fraction of an ounce as it ever
was, but I don't think selling cannabis in imperial units is any more
illegal than just selling cannabis

same in NZ - pounds and ounces for cannabis. Everybody uses imperial for
height still, and newborn babies are in pounds & ounces...

Tim
--
Love is a travelator.

 

[Paul Burridge]

On Tue, 4 May 2004 15:01:12 -0700, "Terry Given"
<the_domes@xtra.co.nz> wrote:

same in NZ - pounds and ounces for cannabis.

I had no idea there was such a enormous consumption of dope in NZ. In
Britain, no one other than a dealer would buy lumps of the stuff that
size.
--

The BBC: licenced at public expense to spread lies.

 

[Paul Burridge]

On Tue, 04 May 2004 01:55:47 GMT, john_c@tpg.com.au (John Crighton)
wrote:

Yes, I know that unit, I have a 2001
Repairing that unit is not dead easy for hobbyists.

Hey, I must be semi-pro by now, with all the info I've been given over
the last 2 years.
I'm screwed without a circuit diagram, anyway. Some people never seem
to need 'em but I've never understood how they manage. Given a
diagram, I'm actually surprisingly good at fault-finding.

I am assuming that AVO at Dover were useless with your
enquiries regarding information on the AVO CT378B

I just assumed they'd blank me on the age of it - like Tektronix - and
try to sell me one of their new ones (assuming they still make SGs,
that is).

If you wanted a good back up signal generator,
that is dead easy to repair. Here is one for sale.
Marconi TF 144H 50 ohms output Z. BNC connector.
10KHz to 72MHz
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&category=40004&item=3094746090&rd=1

Thanks, I'll take a look later 2day after I've downloaded the update
for this latest virus that attacks your system via web portals.

I like that model, for a number of reasons.
Very stable frequency wise (when warmed up).
It has that nice smell inside that you get from valve gear. LOL
Everything inside is getatable.

Yeah, but what if one of those hard-to-find toobz goes tits-up?

Big knobs and easy to read dials, good for failing eyesight.
When the attenuator gets smoked by accidentally pressing a
microphone push to talk button of a transceiver under repair
on the bench, it is very easy to replace the resistors in the
attenuator.
It was not that heavy that I couldn't hump it up the gangways
of ships, decades ago, to do radio service work but it is way too
heavy for me now. Heh heh heh...

You might like to check out how far away that unit for auction,
is away from you. I wouldn't pay any more than 45 quid.
Even 25 quid is right on the limit for me. But if no one bids
you could get lucky. I bought one here in Australia for $10
at a Ham fest.

I only mentioned the TF144H incase you were looking for a
good cheap sig gen to accompany your TF2002AS do some
serious radio receiver work. Both have good attenuators.
Having two good signal generators would help you out with
all that filter and interference work that has been plaguing you
over recent months. One sig gen as the desired signal, the
second sig-gen as the interfering signal etc.

Sounds like a great idea, actually. The problem is of course that even
here we're hardly spoiled for choice IRO older test equipment. Finding
one of those particular models for sale in this country would be
tricky, I'd imagine. Anyway, I'm about to mail you a pic of the AVO,
so keep an eye open in your inbox and don't delete me as spam!
Admire those classic 1950s lines.....
--

The BBC: licenced at public expense to spread lies.

 

[John Crighton]

On Tue, 04 May 2004 13:56:24 +0100, Paul Burridge
<pb@notthisbit.osiris1.co.uk> wrote:

On Tue, 04 May 2004 01:55:47 GMT, john_c@tpg.com.au (John Crighton)
wrote:

Yes, I know that unit, I have a 2001
Repairing that unit is not dead easy for hobbyists.

Hey, I must be semi-pro by now, with all the info I've been given over
the last 2 years.
I'm screwed without a circuit diagram, anyway. Some people never seem
to need 'em but I've never understood how they manage. Given a
diagram, I'm actually surprisingly good at fault-finding.

I am assuming that AVO at Dover were useless with your
enquiries regarding information on the AVO CT378B

I just assumed they'd blank me on the age of it - like Tektronix - and
try to sell me one of their new ones (assuming they still make SGs,
that is).

If you wanted a good back up signal generator,
that is dead easy to repair. Here is one for sale.
Marconi TF 144H 50 ohms output Z. BNC connector.
10KHz to 72MHz
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&category=40004&item=3094746090&rd=1

Thanks, I'll take a look later 2day after I've downloaded the update
for this latest virus that attacks your system via web portals.

I like that model, for a number of reasons.
Very stable frequency wise (when warmed up).
It has that nice smell inside that you get from valve gear. LOL
Everything inside is getatable.

Yeah, but what if one of those hard-to-find toobz goes tits-up?

Big knobs and easy to read dials, good for failing eyesight.
When the attenuator gets smoked by accidentally pressing a
microphone push to talk button of a transceiver under repair
on the bench, it is very easy to replace the resistors in the
attenuator.
It was not that heavy that I couldn't hump it up the gangways
of ships, decades ago, to do radio service work but it is way too
heavy for me now. Heh heh heh...

You might like to check out how far away that unit for auction,
is away from you. I wouldn't pay any more than 45 quid.
Even 25 quid is right on the limit for me. But if no one bids
you could get lucky. I bought one here in Australia for $10
at a Ham fest.

I only mentioned the TF144H incase you were looking for a
good cheap sig gen to accompany your TF2002AS do some
serious radio receiver work. Both have good attenuators.
Having two good signal generators would help you out with
all that filter and interference work that has been plaguing you
over recent months. One sig gen as the desired signal, the
second sig-gen as the interfering signal etc.

Sounds like a great idea, actually. The problem is of course that even
here we're hardly spoiled for choice IRO older test equipment.

Finding
one of those particular models for sale in this country would be
tricky, I'd imagine.

WHAT! YOU ARE KIDDING ME!
ARE YOU STILL ON THE PISS?
It is a bleeding Marconi. I thought they were made in
Chelmsford. That is just up the street from where you
are in London, by Australian standards of distance.

The unit I have been going on about is for sale in Beds UK.
Where is that? Bedfordshire maybe. Four streets away
by Australian distances. Current bid 0 bids. 25 quid.
You didn't even look. Cripes.....tearing hair out.
C'mon Paul, sober up.
Regards,
John Crighton
Sydney