RF unit 25 10d/1016 What is it from?

[greasylox]

About 10x6x4 inches, front panel with 5 position ceranic yaxley type switch running the lenth if the case, 3 x octal valves, metalised coating flaking off, unable to ident. several very nice ceramic coil formes inside.

Can anyone identify what it was part of, loathe to pull it apart just in case its more usefull to someone as is, rather than more bits for my junk box.

[llama]

Part of the Gee radar system, plugs into an R1355 IF strip which all connects to an indicator 62A.

Useful for frequency down-conversion and for anyone building the interior of a Lancaster.

Graham

[G6Tanuki]

It's a "RF Unit" from the WWII "Gee" airborne navigation system.

http://www.duxfordradiosociety.org/r...355/r1355.html

http://www.jproc.ca/hyperbolic/gee.html

Different "RF" units gave different frequency-coverage. In the immediate post-WWII-era they were popular with amateurs as VHF converters.

Your octal-valved version is the lowest-frequency one: the valves are likely to be the military version of the Mazda SP61 pentode. Other models - operating at higher frequencies - used the famous EF50.

[dave walsh]

Sounds like the war time plug in units 24/25/26 [ex aircraft comms] then subsequently sold as surplus to use as various SW convertors or to strip for parts. I don't think there are many intact ones left [I used to have a couple-perhaps still do]. Too good to strip down these days I imagine.
Dave W

Snap! Crossed with the proper info!

[turretslug]

It sounds like a front end module for a WW2 airborne navigation unit known as "Gee". (Search engine time!) It compared the times that synchronized pulses from widely spaced transmitters arrived at the receiver, the operator determining the aircraft position from pre-calculated charts. It could be described as the grand-daddy of GPS!

Someone will probably express interest, lots were kicking around in the years after the war but they're not so common now, I believe many were modified as Band I,II, even III tuners, amateur radio VHF use and so on.

[Anthony Thomas]

What sort of price would these units fetch these days?

[llama]

Last one I bought off ebay, less valves, cost me about £15.
Graham

[dave walsh]

I remeber a couple of PW Converter articles. Wasn't the IF about 9 meg Graham making it handy to front end any set with a fairly standard SW range or am I making that up?
Dave W

[greasylox]

Thank you everyone for the mass of replies, now that I know what it is the question is what to do with it. I'm open to suggestions.

dave

[Anthony Thomas]

A retro aerial tuner for a replica Argus television perhaps using an article from FJ Camms' book "Practical Television Circuits" perhaps?

Tony

[llama]

To Dave in particular - I think the IF is 7.5 Meg so around that area anyway. Back in the '60s I wanted to extend the coverage of my R107 and used the RF24 version which covered 20 to 30 Meg and that enabled me to hear some good DX on "15".
BTW: RF25 is 40-50, RF26 is 50-65, RF27 is 65-85
Graham

[dave walsh]

Thanks Graham yes around 40 metres rings a bell. Some convertor designs required the master set to pick up a more obscure IF but most sets domestic/professional covered 7 Megs on SW so these units were handy!

Coicidentally [re post 3] some mags from the recent Audiojumble have turned out to be Duxford Radio Society from 2001, showing the Lancaster body reconstruction and Gee System then recently installed.

Dave W

[dave walsh]

Noticing that you have now "inherited" the RF 25 Graham, reminds me that I spotted an article in the Xmas RSGB Bulletin Volume 29 No 6 [December 1953] in which an RF 24 is utilised to create a"Convertor for 21 Mc/s". The author notes that "most Government surplus receivers have an upper limit of 18mc/s". I bet he didn't expect interest in 2013 almost exactly sixty years later.

The article confirms an IF output at 7-5 Mc/s. I never could remember the ranges but the VMARS manual for the tropicalised versions [on line] is very good and well illustrated saying that the 24 [20-30meg] and yours [40-50] are click stop tuning. Hence the 24 gets a bandspread arrangement. The 26 [50-65] and 27 [65-85] already have variables. I suppose you will know all this but I've just put it up for others interest. Perhaps the 25 could be modded to reach 5 metres but Im guessing the 24 was the one in demand in those far off days!
Dave W

Just spotted that you had put the ranges up already-a senior moment as the Americans say.

[Anthony Thomas]

Below should be a thumbnail of my three RF24 Units, one original, one partialy robbed for parts and one modified.

I was checking how the GEE worked and was wondering if this operated on the same principle as the LORAN APN-9 as the Loran APN-9 compares two traces on a 3BP1 cathode ray tube. Can anyone expand on this?

http://www.usaf-nav-history.com/Tools/APN-9%20LORAN.jpg shows image of Loran APN-9.

http://www.jproc.ca/hyperbolic/lora_scope.jpg shows image of how the loran trace is interpreted, the difference between the time "blips"

I have always thought that these two systems worked in a similar manner but was told this is not so.

The Loran staions were closed years ago now but I did manage to get one of my three Loran APN-9 recievers to give a readable trace, this was in the late 1970s. I have a rotary converter that converts 24 Volt to (ca) 115 V 600 cycles.

Tony