UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Test Gear and Workshop Equipment

Notices

Vintage Test Gear and Workshop Equipment For discussions about vintage test gear and workshop equipment such as coil winders.

Reply
 
Thread Tools
Old 13th Jun 2018, 9:38 am   #1
stevehertz
Dekatron
 
stevehertz's Avatar
 
Join Date: Sep 2011
Location: Rugeley, Staffordshire, UK.
Posts: 3,525
Default Scope specification for FM use?

I have a Gould Advance OS250A-TV 10MHz scope. I recently found it 'wanting' when fault finding and setting up a hifi FM tuner. I'm looking for advice regarding a suitable specification (not necessarily models, although that too) for a scope that would be able to do all that is needed to setup an FM tuner without struggling? I'm not sure even what parameters the spec would include, but maybe bandwidth, input impedance (?) etc. I don't want a valve scope (too big) no matter how cheap, readily available etc. Thanks.
__________________
A digital radio is the latest thing, but a vintage wireless is forever..
stevehertz is offline   Reply With Quote
Old 13th Jun 2018, 11:09 am   #2
Radio Wrangler
Dekatron
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 10,926
Default Re: Scope specification for FM use?

10.7MHz for the IF, but it would be good to have several harmonics so you can see IF waveforms being compressed by the limiters so a 50MHz scope works well unless you want to see the local oscillator. Scopes don't stop dead at the quoted bandwidth, that number is the minimum frequency of the 3dB point. A 100MHz scope will show the LO signal and the RF (if the latter is big enough) though the voltage measurement accuracy will be a bit off.

I've used 50MHz and 100MHz scopes and never had any problems.

On the second hand market, they all seem to be in the same price bracket, so you may as well have something decent.

Tek scopes like Fluke meters carry premium prices.
HP scopes are good and lack the Tek premium price because there is a legend that HP scopes don't trigger. Oddly, all mine have no problems and the legend lets me pick them up quite cheaply. Hameg are Rohde & Schwarz and are good too.

The Tek 465 family and the HP1740 are quite portable and fairly small, and are pretty comprehensively equipped. The HP doesn't need a fan, while the Tek fan can be a bit noisy in a quiet room. I have a couple of each.

Philips made some reasonable ones and some not so good ones, but I don't know my way around them. The old Cossor CDU150 is reasonable. But there's a good following on here of Tel?HP/Hammeg so knowledge and the odd part are available.

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is offline   Reply With Quote
Old 13th Jun 2018, 11:39 am   #3
Leon Crampin
Octode
 
Join Date: Nov 2005
Location: Surrey, UK.
Posts: 1,344
Default Re: Scope specification for FM use?

A very good summary above, in my view.

Analogue scopes are old now, so any instrument you buy needs to have a good build standard with good quality components, and above all, excellent documentation backup. Specific spares are always going to be a problem, but the more common 'scopes are a better bet for finding a donor instrument when spares are critical.

For build quality, I would only now consider Tek or H-P. The Brits (Gould, Cossor etc.) used such poor components that they are now more trouble than they are worth.

For documentation, Tek are king - but I give all credit to H-P and have found their manuals excellent, but a bit harder to find.

Performance wise, Tek (especially) and H-P (generally) work to spec and are stable and good to use. If you need options such as 12/24V DC power, Tek generally gave a wider choice.

I did fall foul of the celebrated H-P triggering "myth" when working on diesel engines with the scope powered from an inverter in a very noisy electrical environment. The Tek 465 saved the day, and distinguished itself by operating faultlessly when perched on a 12 cyl diesel engine in the rain, powered by a somewhat erratic inverter. I've been an admirer of Tek scopes ever since.

The H-Ps always worked perfectly well in the lab and I couldn't fault them - but scope driving is habit-forming and once you find your favourite, you're drawn to it. I would buy a suitable H-P scope for lab use without hesitation. It might be cheaper than an equivalent Tek.

Finally, avoid any later scopes which use application specific chips. They are all too easily written off for lack of spares. For my money, the Tek 465 would be my favourite, but I also have its smaller brother the 453 here which is a gem, with a pin-sharp trace. I use this scope a lot.

Leon.
Leon Crampin is offline   Reply With Quote
Old 13th Jun 2018, 12:27 pm   #4
David G4EBT
Dekatron
 
David G4EBT's Avatar
 
Join Date: Feb 2003
Location: Cottingham, East Yorkshire, UK.
Posts: 3,342
Default Re: Scope specification for FM use?

I'm quite a fan of Hameg scopes - they were the largest selling range of scopes across Europe including the UK in their day and were widely used by schools, colleges, universities as well as in labs and service workshops. For some years now I've had a Hameg 203-7, for which the documentation is available. They're dual trace and the bandwidth is specified as 20 MHz, but that said, it performs well beyond that range. Attached below is a trace of a 55MHz sine wave on my 203-7. Can't really ask for more than that from a 20 MHz scope.

As an added bonus they have a built-in component tester. Also, a square wave calibration facility switchable for 0.2V/Div to 2V/Div

Because they sold is such large numbers, they appear frequently on e-bay. A 203-7 would typically be £65 upwards in good cosmetic and working condition. Personally, due to their fragility and risk of damage at the hands of couriers, I'd only every buy scope on the basis of 'inspect and collect and pay cash on collection'.

There will be those who may suggest buying one of the many small digital scopes that seem to abound these days, but I think that for most of us, whose requirement for a scope is limited and occasional, a good quality analogue scope with solid track record adequately meets our needs.

I've attached a diagram which shows the front panel controls layout.

Hope that's of interest.
Attached Thumbnails
Click image for larger version

Name:	Pic 14 55 MHZ on 20MHz Hameg 203 7 scope.jpg
Views:	79
Size:	60.7 KB
ID:	164507   Click image for larger version

Name:	Hameg Scope front panel.jpg
Views:	62
Size:	100.9 KB
ID:	164508  
__________________
David.
BVWS Member.
G-QRP Club member 1339.
David G4EBT is online now   Reply With Quote
Old 13th Jun 2018, 1:52 pm   #5
PJL
Dekatron
 
Join Date: Sep 2005
Location: Seaford, East Sussex, UK.
Posts: 3,875
Default Re: Scope specification for FM use?

It's obviously useful to have a faster scope but keep in mind that the probe capacitance is an issue when working with tuned circuits. A good signal generator with a reasonably wide sweep would be first on my list. A low capacitance RF probe for your existing scope would also work for you and these can be home made.
PJL is offline   Reply With Quote
Old 13th Jun 2018, 2:34 pm   #6
Radio Wrangler
Dekatron
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 10,926
Default Re: Scope specification for FM use?

You can also use scope probes backwards, the BNC end attached to the output of a sig gen and the grabber snagged onto a bit of circuitry you want to inject into.

Not calibrated in any way, but a quick and dirty way to inject a bit of signal with minimum disturbance.

Get a good scope. Keep your eyes open for good probes and buy them when you see them.

DO NOT BUY one of those switched x10/x1 probes. Go for fixed x10. The fixed probes outperform the switched ones quite handily, and it avoids you moving the switch accidentally. You'll very rarely need a x1 probe. Having a separate one is no bother,

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is offline   Reply With Quote
Old 13th Jun 2018, 4:50 pm   #7
dave cox
Octode
 
dave cox's Avatar
 
Join Date: Jan 2009
Location: Bristol, UK.
Posts: 1,196
Default Re: Scope specification for FM use?

Will you be wanting to 'sweep tune' the IF stage ?
This may put constraints on triggering capabilities and may also depend on your signal generator. Will the signal generator free run with the scope triggering or have the scope free run while triggering a sweep

I must confess that having enough bandwidth to see the RF (in an FM tuner) didn't help me as the signal was too small

Occasionally, I see the unpopular / heavy / large tek 7603 going for little money, but you need to pick one with suitable plugins ...
dc
dave cox is offline   Reply With Quote
Old 13th Jun 2018, 5:29 pm   #8
Radio Wrangler
Dekatron
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 10,926
Default Re: Scope specification for FM use?

If you're using a sweeper/wobbulator you just get the sweep from the signal generator and use the scope in X-Y mode. Most have that and the HP/Tek jobs usually let you adjust the X gain to fit a picture to the screen. No triggering required and this way if the sweep oscillator in the generator isn't a good linear sawtooth, it doesn't matter.... some sweep sinusoidally

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is offline   Reply With Quote
Old 14th Jun 2018, 1:01 pm   #9
stevehertz
Dekatron
 
stevehertz's Avatar
 
Join Date: Sep 2011
Location: Rugeley, Staffordshire, UK.
Posts: 3,525
Default Re: Scope specification for FM use?

Quote:
Originally Posted by PJL View Post
It's obviously useful to have a faster scope but keep in mind that the probe capacitance is an issue when working with tuned circuits. A good signal generator with a reasonably wide sweep would be first on my list. A low capacitance RF probe for your existing scope would also work for you and these can be home made.
Can you give me a model name or a link to such a probe please? Looking on the auction site I get a load of 'kit type' parts come up. I'd rather buy something that is plug and play. Thanks.
__________________
A digital radio is the latest thing, but a vintage wireless is forever..
stevehertz is offline   Reply With Quote
Old 14th Jun 2018, 1:07 pm   #10
stevehertz
Dekatron
 
stevehertz's Avatar
 
Join Date: Sep 2011
Location: Rugeley, Staffordshire, UK.
Posts: 3,525
Default Re: Scope specification for FM use?

Thanks everyone for you input, much valued and appreciated.

My new sig gen - yet to used - is the hallowed HP8601A. I have performed AM alignment many times including IFs using an old but good Advance sig gen. For FM alignment I have been aligning using weak stations at each end of the scale and not bothering with IFs to date. But now I want to start doing things properly. So, that's what I need a better scope for, one that works well with no foibles and triggering issues for that stated purpose, and doesn't run out of MHz!
__________________
A digital radio is the latest thing, but a vintage wireless is forever..
stevehertz is offline   Reply With Quote
Old 14th Jun 2018, 2:27 pm   #11
John10b
Heptode
 
Join Date: Nov 2016
Location: Aberaeron, Ceredigion, Wales, UK.
Posts: 739
Default Re: Scope specification for FM use?

I am on the lookout for a scope (see Wanted ).
Any suggestions as to best place to get one (apart from eBay)?
I did take a look at Stewart’s of Reading, and considered the Gould OS250b, but was put off by earlier comments about build quality and “not worth the trouble “ any comments please.
Cheers
John
John10b is offline   Reply With Quote
Old 14th Jun 2018, 6:29 pm   #12
Chris55000
Heptode
 
Join Date: Aug 2007
Location: Walsall Wood, Aldridge, Walsall, UK.
Posts: 534
Default Re: Scope specification for FM use?

Hi!

I can only agree with Tek 465 recommendations, but unless you're skilled in industrial or T & M repair, you must pick a 465 in good working order or advertised with a recently repaired PSU – all Tek Scopes MUST have electrically perfect power–circuits for stable and usable operation – one costing anything less than £150·£250 will need repair as everyone wants them and knows what they're worth in working order these days!

British 'scopes like Gould, Cossor are best avoided because of parts problems, particular cosmetics, however Telequipment are a much better proposition – there's more of them about, and for FM use, something like a D61/D61a will be more than adequate!

Chris Williams
__________________
It's an enigma, that's what it is! This thing's not fixed because it doesn't want to be fixed!
Chris55000 is offline   Reply With Quote
Old 17th Jun 2018, 3:34 pm   #13
stevehertz
Dekatron
 
stevehertz's Avatar
 
Join Date: Sep 2011
Location: Rugeley, Staffordshire, UK.
Posts: 3,525
Default Re: Scope specification for FM use?

Quote:
Originally Posted by John10b View Post
I did take a look at Stewart’s of Reading, and considered the Gould OS250b, but was put off by earlier comments about build quality and “not worth the trouble “ any comments please.
My scope is a Gould Advance OS250A-TV and although I'm trying to upgrade to one with more bandwidth (hence this thread), I cannot fault it for what it is/does. When I worked in a test department we used to use them and they were good workhorse scopes. Re build quality, the guy who I bought mine off did not pack it properly (to say the least) and the handle was broken and the chassis bent. I took it all apart and straightened everything out, and I don't recall it being badly built, on the contrary I seem to remember being pretty impressed. In fact if anyone is after a 10MHz scope I would recommend it.
__________________
A digital radio is the latest thing, but a vintage wireless is forever..
stevehertz is offline   Reply With Quote
Old 17th Jun 2018, 3:37 pm   #14
stevehertz
Dekatron
 
stevehertz's Avatar
 
Join Date: Sep 2011
Location: Rugeley, Staffordshire, UK.
Posts: 3,525
Default Re: Scope specification for FM use?

Can anyone give me the make/model number or a link to a low capacitance RF probe ? In this instance I don't want to make one myself.
__________________
A digital radio is the latest thing, but a vintage wireless is forever..
stevehertz is offline   Reply With Quote
Old 19th Jun 2018, 4:21 pm   #15
dave cox
Octode
 
dave cox's Avatar
 
Join Date: Jan 2009
Location: Bristol, UK.
Posts: 1,196
Default Re: Scope specification for FM use?

Something around 10pF tip capasitance for a X10 probe (10Mohm) is typical. That 10Mohm looks great until you consider the effect of the 10pF shunt at 1MHz which is ~16Kohm Thaks OK if you are probing a 50ohm line but for anything else that loading probably won't be good.

Personally, I wouldn't spend too much on a X10 10Mohm probe as the results for the extra cash maybe not significant for what you want it to do. The only time I notice the difference between a cheap probe and a much better one is, for example, looking at a square wave when the cheap probe will make it look like its ringing !

RS do a range of cheap probes although the ones I looked at were switched X1/X10

dc
dave cox is offline   Reply With Quote
Old 19th Jun 2018, 5:26 pm   #16
John Caswell
Pentode
 
Join Date: Jul 2009
Location: Wokingham, Berkshire, UK.
Posts: 234
Default Re: Scope specification for FM use?

I have just put some scopes up for grabs in the for sale thread

John
John Caswell is offline   Reply With Quote
Reply

Thread Tools



All times are GMT +1. The time now is 12:30 am.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2018, vBulletin Solutions, Inc.
Copyright ©2002 - 2018, Paul Stenning.