Harwell rally 9 February

[high_vacuum_house]

Good morning,
I see that the Harwell rally near Didcot is next weekend. I haven’t been to this event before and am interested in visiting. How does it compare to other radio rallies for size, old equipment, old components ECT.

Many thanks,
Christopher Capener

[MrBungle]

It was excellent last year. I shall be going. Size is fairly large. Main gym sized hall and side rooms. Lots of parts and a wide range of traders.

I didn’t buy anything in the end as I went with a shopping list and a promise I wouldn’t come back with anything large but I had my eye on some tek and HP bits. This year all bets are off .

Advice though: was frozen solid waiting last year and the queue gets pretty big pretty quickly. Get there early and take coffee

[AC/HL]

Added to the calendar: https://www.g3pia.net/

[high_vacuum_house]

Many thanks,
I will try to go along as I have the day free. I recognise some of the traders. notice the start time is 10am. Do they let people in earlier like some rallies or do the gates open exactly at this time?.

Christopher Capener

[Sinewave]

I'll be there, fingers crossed! It is a very good event indeed.

[MrBungle]

No letting people in early on this one. I’m pretty good at doing the grey man thing and ending up inside on these things way before they start but not so on this one

[GrimJosef]

Originally Posted by high_vacuum_house

... notice the start time is 10am. Do they let people in earlier like some rallies or do the gates open exactly at this time?

There's only a single entry time. It's nominally 10:00 although I think they actually opened the doors a few minutes early last year, not least because the folk in the queue were cold. They do the usual thing of coming down the queue beforehand selling tickets, so when the doors open most can just walk in.

Of course if you have a stall you will be allowed entry earlier. Again 'of course' some of the early entrants will be roaming the halls buying up bargains. Those of us waiting in the queue last year watched one chap walking to and from his car putting a succession of interesting items into it. Not very subtle.

EDIT: Worth noting the warning about the power station chimney demolition the same morning. It may well disrupt the main A34 link into Didcot (although the chimney is scheduled to be down before 09:00, and will probably drop well before). It may even close the town's northern perimeter road as the chimney is not very from it and after the debacle with the 33kV power lines when the cooling towers were dropped last year the authorities have become very cautious.

VB

[Ken Taylor]

Further to GrinJosef's message - See the note on the HARS web site about sign posting: https://www.g3pia.net/

If you have a 2m radio or scanner they are providing talk-in. G3PIA on 145.550.

Ken

[G6Tanuki]

Harwell is always one of my favourite rallies: it's close to Rutherford Appleton Labs, the UKAEA Harwell site, and the old JET facility at Culham is just up the road. Which means that you sometimes come across 'interesting' stuff from the sales of silent-key types who worked at these sites in the 50s 60s and 70s, who were clearly not averse to pocketing a few of those new-fangled semiconductor-devices from work to use in their amateur-projects.

If you're into first-generation Germanium transistors etc, it can be a good place in which to pick through the 'under-the-table' boxes of nondescript circuit-boards etc.

A couple of years back, the old valve 1970s/1980s 28MHz GB3RAL beacon-transmitter [built around a repurposed pager-transmitter] appeared on one of the stalls as part of the general scrap.

[Sinewave]

It's a windy one! Just plotted up in the car park ahead of time as I were elsewhere this morning already.

[G6Tanuki]

Yes - it was vey windy! I dropped in very briefly [could only spend 20 minutes or so looking round because I had to go to Oxford to return the dog who's been staying with me for a couple of days].

I came away with an AEL3030 HF SSB transceiver for £10 (it's got 3 crystal controlled channels - one is already on 80 Metres!), a batch of 2N3819 FETs, and some ferrite toroids/binocular transformer-cores so I can do some more dabbling with direct-conversion receivers.

Overall there seemed to be fewer stalls than in the past - the walkways between the stalls in the middle of the main hall were noticeably wider than in previous years. "Interesting" radios spotted were a bunch of BC343/348-type WWII US Military receivers, a CR100 and a couple of HROs.

[MrBungle]

Did really good today. Managed to grab a working Tek 2445, an unknown HP 3400A, a couple of ARRL books, one from Mr Hayward I’ve been after for about a year. Very happy.



Tek is immaculate after a brush down



Edit: meant to say. The A4130 was dangerous. Bits of tree all over it. Only disappointment was at a garage on the way there they had a power cut in the middle of trying to buy a drink!

[Aub]

Must be nice to have so many rallies, etc not too far away. There are only a couple round this neck of the woods, as far as i know.

Cheers

Aub

[GrimJosef]

If it's any consolation I'll be driving all the way up from here (I live about 700yds away from this morning's 'Harwell' event) to Warwickshire in three months or so for this https://www.retrotechuk.com/. Next weekend I'll be heading over to Kent for this https://www.audiojumble.co.uk/. Some events are close. Lots are a long way away.

Cheers,

GJ

[Sinewave]

I spoke to a chap today who picked up an Avo I'd never seen before. Some specialist white Avo in a white case, a largish instrument.

A few goodies spotted, but I remained rather restraint this year.

[high_vacuum_house]

Managed to get there in the morning and dodge the tree debris along the way!!. I bought an unusual Teslameter for £2. Will make an ideal project box. I found some BSX20 transistors on a component stall which I have been looking for repairing a Philips oscilloscope. Other than some components, a Pilz safety relay, a free knackered Roberts radio and a few vintage magazines I think it was worth the drive down.

Christopher Capener

[mark2collection]

Originally Posted by MrBungle

an unknown HP 3400A

Mr B, that yellow sticker looks familiar.

'Uncalibrated Equipment, Not to be used for quality assurance work until registered for such work' Or something along those lines (Am looking via a tiny screen!).

Have a look around the instrument casework for a BLDG number or a H number. Almost certainly from AERE et al on the Harwell site.

If you would like a replacement sticker …

Sadly, couldn't make this years event.

Mark

[MrBungle]

Ah yes there was the remains of one on the back. I’m ashamed to say (well I’m not really) that this is going to be a factory restoration assuming enough of it works that is. I’ve started the process of cleaning it already.

I think I will dig out the Geiger tube and the counter and give it a once over

[Pamphonica]

According to the organisers yesterday's event showed only about half the normal attendance. Not surprising given the wild weather, especially on the way home.
On our way to Harwell we were stuck on the A329M from Bracknell to the M4 for well over an hour while a fallen tree was removed.
I sold a few bits on a mate's stall and came away with a handful of small items, and had a good, sociable day.
-Jeremy

[Radio Wrangler]

The HP 3400A is a true RMS AC voltmeter using a thermal converter pair in a feedback arrangement.

The converter pair is in a round metal can and is irreplaceable. Don't chuck it away if you decide to recycle the case, meter etc, there may be people looking for one because they got used in various other instruments.

They use twin load resistors, each with a thermopile - a series of hot junctions attached to them. Incoming signal (direct or via an amplifier) heats one resistor. A DC amplifier heats the other. The DC amplifier is driven by the difference in thermopile voltages so the DC amp's resistor tracks the temperature of the signal resistor. As the two sectiona are carefully matched, the DC voltage into the amp's resistor must match the true RMS into the signal's resistor.

A second generation one came out in the early 80's built as a sort of MEMS structure and fitted into a TO-5 type can. 1SB1-0021 if my memory serves.

David