Hi David

 

Chris G3XIZ can always copy me as can Dennis M0JXM.   I might get down to the wilds of Hitchin with MOFMT too!

 

Looking at the weather its a bit blowy today, but I may venture out and reconnect Inverted L and loading coil for MF.

 

If I can get the garage snug with fan heaters then I will look at patching in the new Hafler 9505 and get a bit of QRO going for Saturday from 2pm onwards.

 

Kit here is :-

 

ELAD FDM Duo as a the sig gen, giving out 630m signals via the 0dM transverter port (this is good for 1khz up to 250mhz!) ,

 

Then routing through either a cheap Chinese 1w broadband amp off Ebay (I’ve learnt that these let the magic smoke out easily if abused or badly connected, so buy a few)  or the G3XIZ designed and built interstage amp (a work of art in veroboard and aluminium boxing and remarkably immune to my novice clumsiness)

 

The coax then heads out of the shack via the old tumble dryer vent (it was our old kitchen) and then 10 metres across backyard into garage.

 

Coax then is fed into input of a Hafler P4000 and soon to be Hafler 9505 via the input transformer   http://www.w1vd.com/Haflertransformers.html 

 

See also the excellent pages http://www.w1tag.com/XESTX.htm  http://www.w1vd.com/9505MF.html http://www.w1vd.com/page23.html

 

The stereo speaker outputs of the Hafler are bridged to give about 200w for the P4000 and 400w for the 9505 @ 473khz.

 

EU spec (220v) Haflers come up on Ebay from time to time, albeit rarely.  P4000s are about £250 and I got my 9505 for £400. 

 

The speaker output is  connected to a home brew 4:1 balun to give around 30 ohms impedance into coax cable from an 8 ohm output  http://www.w1vd.com/Haflertransformers.html 

 

This coax runs a further 5metres from garage to fence, with the coax core being attached to the bottom of  a home brew tapped loading coil.  (about 190 turns on a 6” soil pipe former).

 

The antenna from the tap point  is a 10m vertical (subject to wind!) wire  on a roach pole (lashed to fence with cup hooks and cable ties)   with 3 x 30m top wires, strung over roof of house to a 10m roach pole at bottom of garden

 

The braid goes to earth which is a series of cross bonded earth stakes, oil tank feeder pipe, buried  steel meshes under back patio and block paved drive.

 

Resonance and tap point  is measured using a RigExpert AA1000 analyser set for 473khz with a 50khz range initially and then bracketing down to 5khz range (minimum) to get best figures for impedance, reactance & return loss.  -20dB or more is feasible and I’ve seen -30dB. 

 

At the shack end, the ELAD is natively configured as a Kenwood TS480 and is run through HRD5 (last freeware version) on a Dell 1749  I3.   For CW/Data I use the excellent DM780 that comes bundled with HRD5.

 

The ELAD sets itself up as a USB soundcard and I use the “MCW” mode to generate CW tones via USB so with a ~ 1.1KHz offset.  I tune to 471.9khz and my CW signal appears at about 473khz.

 

The “USB” soundcard is a little “moody” to say the least and takes the occasional “uninstall and re-install” via control panel before it starts to show the waterfall display properly.

 

The receive signal is fed in via Ant 1 (SO239) from a long wire.  Ideally I need to build another loading coil and inverted L for Rx or use a loop or miniwhip as the noise on the longwire is the usual S7 and kills all Dx signals.

 

Prior to the interstage/hafler approach I used the vertical for both Tx and Rx with an IC706mk2G (broadband modded, easy diode snip).   The IC706mk2g will give about 10 watts out on MF and interfaces nicely with HRD/DM780 too.

 

Using this arrangement, I regularly got CW/QSOs out to ~ 100 miles and using WSPR, could be spotted out to 2000km occasionally and 1000km routinely and on the Rx side I could pick up spots from 2000km away.

 

The interstage approach precludes the use of the Tx  antenna for RX so its a new L or a miniwhip I think.

 

I’ve also used an IC735 which will generate 5w of RF at 470khz and the RX is suitable sensitive too.  An alternate Rx system is a Datong VLF converter which upconverts to 28mhz.  This works very well and is what I’ve used to Rx SAQ and also in VLF experiments.

 

 

I’ve tried the ELAD/Hafler arrangement on 8.97 khz and using my inverted L and some daisy chained LF coils been able to hear my 5 wpm CW signal about 500m away using a simple vertical in the car.   I’ve also tried using the G3XBM earth mode approach https://sites.google.com/site/g3xbmqrp/Home/earthmode and got a similar range.  G3XIZ was unable to detect any signal though at 2 miles distant, but thats no surprise and my Tx antenna was hugely a compromise.

 

I’m not a tech expert by any means (my field of work is paediatric oncology and biotech), radio is just a hobby when work permits!

 

My local “Elmers” are Chris G3XIZ (loaned me and built me no end of kit) , Dennis MOJXM, Pete  MOFMT, Dave G4GIR, Roger G3XBM, Chas, Larry G4OXY (fixed the blown Datong!) and back in my early days of MF’ing Jim Moritz M0BMU.   Sparring with Mal G3KEV has also been great fun, though I cannot hope to compete with his monster station.  A QSL card from EI0CF is on my pin board  from a CW QSO in 2010.    Stefan, Rolof, Graham, John Andrews, Jay Rusgrove  and many others have been a great help too.

 

This MF stuff can be very addictive, especially when the spots are low and much above 20m is dead and 20m is a contest zoo.

 

Well, the wind seems to be abating now, so I’ll put a pullie on and venture outside to see if I can fire up the MF show for tomorrow

 

Have a great 2018 all, be safe on roofs, ladders and up trees.  Measure twice and cut once. Check the power is really off and keep one hand in the back pocket if in doubt!

 

 

 

with best regards

 

 

Jim

 

Dr. Jim Cowburn G7NKS     IO92ub

 

Biggleswade  UK

 

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