Re: {Collins} Two-tone test generator?

Hi Chris,

I ran with a used Kenwood SM-220 for a few years, choosing it over the later SM-230 because of the implemented trapezoid function, which I considered a "must have" when operating with a linear amplifier.  Like a number of other posters I find a monitor scope to be invaluable and consider it a pity that they are not more widely used.

Regarding the two-tone oscillator, a properly adjusted Collins 32S-3 (for example) produces IM3 products in the region of -40 dBc and the rather high harmonic distortion of many 'old style' tone oscillators is something of a distraction on a spectrum analyser trace. A link to the Elecraft kit oscillator was posted earlier and I've found that to be a nice unit, with measured harmonic distortion to be a respectable -55 dB or so.

It's not going to match a classic Collins station but if you are buying a digital power meter, I can recommend spending a little extra and buying a Telepost LP-500 or LP-700, which is also a digital station monitor and pseudo spectrum analyser.  The directional wattmeter is accurate, the station monitor time domain functions work very well (and include flexible trapezoid and half trapezoid), and the pseudo spectrum analyser is good enough for the proud Collins owner to demonstrate the superiority of the S-line over nearly anything else, ancient or modern. The Telepost unit has a built-in, low-distortion two-tone oscillator, the output of which is selectable via my audio panel to allow quick evaluation of all radios on the desk.  One minor comment is that the test tone output could usefully be more flexible in terms of level and galvanic isolation but any limitations are easily dealt with in practice.

73, Peter (VK6HP).     

-----Original Message-----
From: Collins <> On Behalf Of Chris Mortlock via Collins
Sent: Monday, 12 August 2019 3:13 PM
To: <collins@xxxxxxxxxxxxx> <collins@xxxxxxxxxxxxx>
Subject: Re: {Collins} Two-tone test generator?

Hi Dale,

I've worked on both the earlier TM-220 and the later TM-230 (slightly larger screen but pretty much the same functionality) and both are fitted with two tone test generators. Indeed I happen to have TM-220 on the bench at the moment for repair!

Tone outputs are switchable (one low tone, one high tone - or vice versa or of course two tones) and both have output on the front (3.5mm for the
SM-220 and BNC for the SM-230) - other than that they are pretty much the same.

Obviously (!) these aren't able to be converted to a 'Collins' look alike - I think that's a great idea - one I will be looking at if I can find a reasonably priced one here in Europe.

You've 'jogged' my memory I recall seeing the idea (pre collins collection interest!) - still remains a good one :)



On 12/08/2019 04:05, Grayson Evans via Collins wrote:
> That is not a bad idea Dale.
> I just bought the panadaptor version on ebay.  I will keep looking for monitor scope for $25.  I didn’t know it had the two-tone built in.  Great Idea.
> 73 Grayson, KJ7UM
>> On Aug 11, 2019, at 5:14 PM, Dale <svetanoff@xxxxxxxxxxxxx> wrote:
>> Grayson,
>> There is a very handy test box that not only provides 2 correct test 
>> tones, but it also allows you to see the output RF envelope from the 
>> transmitter.  I am talking about the Heathkit HO-10 and SB-610 output 
>> monitor scopes.  (Note: several SB-610s have been customized into 
>> matching Collins S-Lines by interested parties.)
>> IMHO, no one using an external amplifier for SSB operation (or the modern digital modes, for that matter) should be on the air without an RF output monitor so you can observe he waveform and KNOW when you are flat topping or having any sort of irregular output.  I own four of the SB-610s and find them to be very useful.
>> Built into each one (and the earlier HO-10 monitor scope) is a two-tone generator that delivers one or both tones at correct levels to insert into your rig's microphone input.  Those tones help with xmtr adjustment and the scope itself helps to actually observe the output waveform from the amplifier.  You can also set it up to do a linearity test between the exciter and the amplifier.
>> If you decide to get one, make certain that you get the manual.  It gives lots of helpful suggestions and most importantly, has representative samples of correct and incorrect RF output waveforms.  My guess is that not enough hams took advantage of these wonderful instruments when they were around or they failed to understand how they help with correct operation. In my case, when driving the 30L-1 with a 32S-series xmtr, no problems once ALC is set properly.  However, when I drive a 30L-1 with a Heathkit HW-12 which has no ALC feedback from the amplifier, I have to watch for flat topping because the HW-12 can easily overdrive the amp and cause on-air problems.
>> Oh yes, a hint about the SB-610: the sweep circuit uses a 6C10 3-section Compactron triode.  That tube is also used in certain guitar amps and so the price has gone thru the roof.  I recently bought 1 as a spare for $25, but an even better deal is to find a 6AC10 Compactron.  I have seen them for $5 and they work about as well.  They are pin-compatible, differing only in gain.
>> I know that both Kenwood and Yaesu made monitor scopes in the past.  I can not vouch for whether they have 2-tone generators or not.
>> 73, Dale
>> -----Original Message-----
>>> From: Grayson Evans via Collins <collins@xxxxxxxxxxxxx>
>>> Sent: Aug 11, 2019 12:34 PM
>>> To: "<collins@xxxxxxxxxxxxx>" <collins@xxxxxxxxxxxxx>
>>> Subject: {Collins} Two-tone test generator?
>>> I am looking for a two-tone test generator to check the output of my 32S’s and 30L-1.
>>> I notice there are a few sold online, but a bit more expensive than I was looking for.
>>> It seems this would be a rather simple app for an iPhone.  I checked the App store but couldn’t find one.
>>> Has anyone found an app that will output two fixed audio tones?
>>> I could homebrew one of course, but all my time seems to be taken up trying to fix my 32s’s!
>>> Thanks,
>>> Grayson, KJ7UM
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