Clansman Centre Junction Dipole

Any Pronto's or Q-Flags about?

The clansman kit had two CJD's - or 'baluns', as civvies refer to them:

1. a "small" one with the 320 which has the typical BNC co-ax connector,
2. a larger one that - iirc- came with the 321 ancils bag, and had a much larger BNC co-ax connector, much like a PL259 in size.

Can anyone tell me what type of balun either was a choke/current, or transformer/voltage balun, and what ratio e.g 4:1, 1:1, 9:1?

I'm presuming - no longer having course notes - that both 320 and 321 expected a 50 OHm load on the co-axial output?

The why? I've got a 320, currently running off a dipole. Just acquired a Kenwood TS530, AT-230 ATU (and possibly a Versa II), and need to construct an antenna or two. Neither the Kenwood nor the AT-230 have a balanced output, so I cant use ladder-line without a 4:1 balun. I can feed a dipole of course, but will need a balun... (or just run it as co-ax end-fed multiband) The "small" balun is in use on the 320, I have a "large" clansman balun, but don't know if this will be suitable.

Anyone know?

It has been a few years but I have a feeling the Clansman CJD's didnt act as a Balum but only as the name, the centre junction for the dipole array to go from feeder (URM 67 typically) to braid/D10 or copper wire.

I do remember using ladder lines and such like with proper balums in South Georgia for the 322's but that is the only time in military use I have come across them.

May be of no help to you but I'm having to think back a winter or two now ! !

Thanks guys.

So, I *could* use either as a vanilla CJD from the coax connector on an ATU

Leg 1 CJD Leg 2
attached to braid outer | | attached to inner cor
coax | |
line | |
ATU | |

If the above makes sense? All I need to do then is take a 320 cox feeder, swap the 90deg BNC/N for a PL-259, and I have a working feed line. Ditto the thicker coax feeder that came with the 321/TURF.

In which case - out of interest - was the balun an issued bit of kit? Never saw one for either the 320/321 that we were scaled for (RE), neither did I ever see ladder line. I feel the need to find one, being an anork^H^H^H^H out of sense of nostalgia :)

Any idea what power the two coax and CJDs were rated for?

You probably have a complete generation of (god knows what name techs are this week) scratching their heads with your use of Ohms law. For the true answer, it is slightly more complex using J notation I believe but I have a slight life so have no idea where to start nowadays.

I find it as an ex Radio Tech I still get blank looks still trying to explain A&P, wavelengths across an antenna and such like.

Anyway to Tiny's request. Balums from what I can remember were never issued as part of Clansman. The 8 wire cage dipoles, unifans and such like I have come across have been in static locations and normally installed by RAF Riggers.

Looking at the solid construction of the CJD, I think as long as you are playing in watts and low hundreds of watts you shouldn't have any issues.
That is why I am not a Foreman and don't have stress in my life ! !

Of course it's more complex, as it's Z, not R in reality. Z is frequency related. However, for poor man's math (perhaps I should have said in the post), using 50 ohms will do. If the answer had been 60A, I'd have said the 321 CJD wouldn't hack a 322. Given the answer was 7A, even with a 100% error, I'm still satisfied the 321 CJD will be good for a few hundred watts of RF.
I'm lost on the P=I2R equation, 250=I2*50, then I cannot be 7, as (7*7)*50 = 2450W Or does the 2 in P=I2R mean something else? P=IR rings a bell.

I always remember V=IR and P=VR (or W=IV as it is referred to now)

Anyway, it wont be fed more than 100W (assuming I ever bother with the full licence... knew I should have taken the Class 1- C&G freebie), its not an issue, simply interested.

I picked up a Versa Tuner II this afternoon, which has PL259, single wire and balanced wire outputs, so I'm not going to struggling any time soon. Thankfully I have no client work due until the afternoon, so have all morning to play :)
Next question - any idea what the connector is, on the large CJD? Its neither PL259 nor BNC... I've got plenty of RG58, RG8, and PL213... but no way of attaching it to the CJD :-(
If this is any help to you, I have CES 43740 in front of me now. The NSN of the Centre Junction Dipole for PRC 320 Basic is given as 5820-99-117-7439 with no other description.
Armed with that... yes it is.

Now all I need is a source of C connector sockets - as the CJD uses a plug - or... anyone still in green kit here who has a buckshee length of "thick coax" for a 321 CJD that they could "donate" for beer funds? :)
Armed with that... yes it is.

Now all I need is a source of C connector sockets - as the CJD uses a plug - or... anyone still in green kit here who has a buckshee length of "thick coax" for a 321 CJD that they could "donate" for beer funds? :)
Have a look on E bay.
It is indeed a C connector.

Basically a larger version of the BNC. The reason it is used is because it is weather proof but not overly bulky.

50 ohm too.

The 320 CJD uses the BNC connector.
Erm thanks.. think we established that its a C connector a few posts back. Do you have any???
Can you spare one or two? Would be nice to utilise this "large" CJD as something other than a paperweight.
And another thought for the ex-R Sisgs instructors.

A dipole has an impedence of 50 Ohms at the centre point, which increases if one off-sets the feed point. I can remember building off-set dipoles, and inverted L's, and using the CJD to feed them... but how the heck did the 320 cope with a change from a 50O impedance to a 300-600Ohm mismatch without a balun using the standard coax and CJD?
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