Very good chaps - yes the trick is to stay away from some resonaces and get others! If it were soley for LF MF Id go in hard and change that out put circuit but dont want to cripple the HF side as I can still use it as a true transverter too - as L89 is accessible from the top of the board I can play pretty easily and try a few things. Changing the drive routing and termination Z will also have an effect which Ill investigate
Ill do some more checking, but what is evident is that as the RX is dang hot at LF/MF its going to be a pretty good addition to the portfolio. Im presently building a 2X drive source from the 10MHz ref which will replace the internal ref osc in the 850 and lock it down - I got the "kit" off Ebay but Im a little shaky with the soldering iron nowadays so Ill see how I do with this SM stuff.
Over the pole - well Im someways in a much better position s/n wise this year though we have new noisy neighbors but using Cardoid or Mults/Beverage I think we are going to do fine.
Ive never got a signal to Eu from here (I cant recall ever being heard further than the poor East coast USA route), but I reckon that its going to do pretty well into VK and ZL and Eu on good N Polar days (rarer this year no doubt) but some ( alot) of the USA will be in a null
http://kl7uk.com/lobes.png - the appx -6dB pattern is estimated but is derived from real time survey coverage from the WD2XDW loop in Oklahoma taken at 7 mile radii back a few years ago - very rough and ready version as I drove with GPS here
http://kl7uk.com/XDWpolar.png
With all these nearby mountains the signal get bounced around in any case so will see what empircally turns sup. (sic) Havnet heard the 510kHz Fairbanks NDB yet this autumn...
Laurence KL1X
Wasilla AK
Date: Tue, 2 Oct 2012 23:50:40 +0200
From:
[email protected]To:
[email protected]Subject: Re: Strefans LF: LF/MF modification of TS850 for LF
Hi Laurence,
Am 02.10.2012 23:20, schrieb Laurence KL7UK:
http://kl7uk.com/850.png
Stefan - heres the part of the circuit concerned - its the coupling
after the 3rd mixer - so its at TX base band frequency, so I can
see perhaps why this C219 could be increased to reduce LF losses, but
not a lot me thinks as the reactance to "Earth" is pretty low at 137 -
the aim is to improve LF without mucking up the HF side so you can only
go so far.
Maybe you can make a series resonance for LF by adding a L in series.
This L must have a C in parallel or a low self resonance frequency. My
first guess...
At least a to high C across C219 will make a almost short cut for HF to
ground...
Still very poor LF and MF - nearly no signals from Siberia/Mongolia on
LF - still at least the snow has stayed away. Loran was around 15dB
down from "average" last nite. Getting very dark in the mornings and a
Huge Male Moose ran into a car on the road into work this morning -
both car/driver and Moose didnt make it.
R. Tell me when the band opens. BTW i'm 3...5 dB stronger since the
last success in december so we may play a lot more this year.
Just played arround with a NE612 for the first time in my life ;-)
Quite useful IC! It became a 475 kHz transmit mixer (460 kHz LO) and is
used in combination with my mechanical filter which i use for MF
RX as well. Then applying white noise from the SpecLab SG i can see the
resonance curve again, now confirming > 50 dB att. in 2 kHz outside
the passband!
73, Stefan/DK7FC
