Re: New Sangean DT-400W


Paul V Birke PEng <nonlinear@...>
 




From: Michael
To: ultralightdx@...
Sent: Thu, May 19, 2011 1:21:59 AM
Subject: Re: [ultralightdx] Re: New Sangean DT-400W

 

Guess I have to give in :-) I only have a SRF-59, G8 and a PL-380 in the uldx range
and am rather fond of the cuteness and sensitivity of the SRF-59. It smiles smugly next to my
ancient
Barlow-Wadley on the shelf... It´s lower sensitivity than the DT-400W is presumably due to the
shorter internal ferrite antenna. Inductively coupling a longer tuned rod makes a big difference, of
course.

Apropos : Things seem to have gone quiet on the ferrite front.
Any new or improved designs in process?


Indeed, have the flat ferrites now (100mm*3mm*20mm) but looking for a large diameter plastic tube dia => 12" to about 20".

This follows directly from Steve's assertion that a large diameter is needed following his experimental evidence posted in this group.


Will place ferrites on each end and wind the contra-winding as per the Polydorroff patents and will be the ~ 1/4" off ferrite surface.

This is the kind of plastic form I am considering

http://www.usplastic.com/catalog/item.aspx?itemid=23849&catid=459

a grounded cage variable capacitor will be used to resonant.
pickup will be via a ~ 24" ferrite rod ( 3 * 8"by 1/2" dia 61 material Amidon0
this will have a contra-winding upon its surface (distance of wire to ferrite surface ~ 1/4")
The idea is that placing this rod in the centre the mutual coupling will be such that it is weak and therefore will not upset the Q of the main tuning circuit yet enough signal for a sensitive radio.

all I have for now Michael
best wishes
Paul in the Northern Colony
VE3PVB


Michael UK - true Brit, ex9Q5TS, admirer of the F-15 and the Harrier, nostalgic for tubes, oops :


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