Burns electronics wavemeter TC-101

[radiograham]

Acquired this wavemeter recently and wondered if anybody knows anything about them or perhaps has one. I would put a pic of it but dont know how.

[AC/HL]

This one?

[Philips210]

Hi.

The case in Bill's pic looks to be similar to my Burns SD-12 Frequency Standard and Burns CC-10 Crystal Calibrator. It might be worth trying to contact Forum member bobfburns who helped me a few years ago with some technical information. I believe Bob used to own/run the company.

Regards
Symon.

[David G4EBT]

That brought back fond memories.

When I was first licensed back in 1974, you had to tell the powers that be (GPO/Home Office?) what test equipment you had to enable you to check they you were operating within the limits of each band, and were not spraying harmonics into your neighbours telly. Like most of my chums back then I said I'd use a Burns TC-101, hoping that the inspector wouldn't turn up on my doorstep to do a 'shack inspection', as they were prone to do from time to time.

Well one day he did turn up and said 'I've come to have a look at your Burns TC-101', so I had to own up and say I didn't have one. He said "I know you don't - I 'm not daft - I just wanted to tell you in the firmest possible terms, not to take the mickey, now put the kettle on". Basically, not 'inspecting' just skiving.

That was a close shave!

Not a very sexy shack back then - just a Pye Cambridge ex PMR transceiver modded to 2 Metres with one transmit crystal and tunable receiver. You called CQ, and said 'tuning high to low' hoping that someone on a different transmit frequency would hear you, so you'd both be able to hear each other's transmissions.

I did later managed to buy TC-101 secondhand, but disposed of it long ago. Nicely built and neat looking.

All a bit of an irrelevance these days, with out-of-the-box, plug 'n play transceivers and no inspections.

[radiograham]

Originally Posted by AC/HL

This one?

Yes thats the one. Do you have one or know much about them. Graham.

[Dave757]

Hi Graham,

For details and a diagram of this wavemeter go to:

www.theskywaves.net/technical.html

This will take you to a page by G8MNY with a massive list of technical info. Go down to Test Equipment, and the Burns wavemeter info is in this section.

Kind regards, Dave.

[AC/HL]

Originally Posted by radiograham

Do you have one or know much about them.

No, I just searched for a picture for you!

[David G4EBT]

There's not really a lot to know about them.

In use, you'd have a homebrew 'RF sniffer' plugged into the input socket, consisting of a length of coax with a couple of turns of wire maybe an inch in diameter, which you'd place near the output from the transmitter. With the key down to emit RF (into a dummy load of course!), you'd tune the wavemeter across the band where you'd expect (hope!) to find the signal, and when the wavemeter is tuned to the resonant frequency, the meter would show a peak. You'd then read the frequency off the dial of the TC-101, and would hope that it corresponds to your belief of what frequency (what band even!) that you think you're on.

If you were on say 3.5MHz, you'd be expected to check if you were also radiating on the second harmonic of 7 MHz, so you'd need to increase the sensitivity of the meter to see if you get any indication of radiating unwanted harmonics. The important aspects back in the 1970s when homebrew was still evident - if only to a small extent - was to be able to check that you were not operating beyond the band edges, that you were no using excess power, and not radiating harmonics. That still applies of course, but those aspects are largely taken care of in modern commercial transceivers.

Digital frequency counters, both commercially made and homebrew have been around for decades, to accurately measure operating frequencies of homebrew transmitters, making instruments such as the TC-101 largely obsolete. I and many others built the Radcom nixie tube digital frequency counter back in 1976, designed by David Pratt who was later to become the C&G Chief Examiner for the Radio Amateurs' Exam. There's a pic of mine below,(checking the dial accuracy of a Heathkit RF-1U signal generator at 100 MHz), along with my homebrew 'RF sniffer'.

As to power output, most equipment in use for many years has been commercially made and with solid state PA stages, often with built-in automatic tuning units, putting out a maximum of 100 Watts PEP on SSB. If a 1:1 SWR isn't seen, the PA stage will wind the power down to protect the PA transistors, so by the time the transmitted RF gets to the feed point of the antenna, it might be more like 50 Watts. Well below the maximum permitted 400 Watts PEP (Not on all bands of course).

So in conclusion, whilst no doubt the TC-101 would still give a good account of itself, to all intents and purposes it's a nice piece of amateur radio memorabilia, but then we could say that about anything from crystal sets to Avos to vintage valve radios.

Just a few 'off the top' ramblings which I hope might be of interest.