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.
I need to move the equipment into the garage from the shack - the garage houses the
W@G Pegglemessers so will do that and take some more meaningful readings, but there is a small increase as yet undefined :-)
- I need to complete the " (not)Transverter" switching mod to allow the RF to come out of the phono socket at the back, but the MF filter, the "fool the logic for all band tx (30kHz to 30MHz) is complete. More as it develops or smokes. I need around 150 milliVolts to get the RF into the Deccas drivers cct
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.
Im keeping this discussion on here as I know a few chaps have the 850's and (maybe) of interest to the wider audience
Laurence KL1X GM4DMA
BP51 IP Wasilla Alaska
Stefan said -
Hi Laurence,
Have you tried to check the increase of the signal voltage at higher
frequencies to see what e.g. doubling of that C causes? Is there no
increase at all?
Do you have the schematic of that section?
73, Stefan/DK7FC
Am 02.10.2012 02:31, schrieb Laurence KL7UK:
Looking for a bit of assistance.
Ive modded my TS850 to allow LF/MF transmit from info from
http://we0h.us/Amateur_Radio_stuff/TS850/ts_850_lf_tx_mod.pdf
(thanks Mike, original by Bob ZL2CA) but the
"supplemental" parallel capacitor value in uF to increase the LF level
isnt mentioned.
Ive actually tried another 0.01 and smaller and higher values but at
137kHz it doesnt appear to increase the level - any takers or
experiences out there who have modded the beast?
We had a load of snow here at the weekend but thankfully its gone
already and Im in the garden pulling up new ropes into 2 Spruce trees -
a bit stronger than the bendy Birch and Ill attempt to pull up the loop
this week. The loop will be slightly bigger, about 50m in length and
slightly higher than WD2XDW in Bartlesville. We will see. COnditions
are lousy at LF and MF given the Geo/Mag at this latitude but I was
hearing Eu on 20m over the Pole pre dawn. We lose nearly 6 mins of sun
per day at this time of year....
Laurence KL1X
"The TS-850 transmit drive to the transverter port is
reasonably broadband as manufactured, and passes
some LF energy for amplification using an external LF
amplifier. It is difficult to modify the TS-850
circuitry to decrease the LF droop without impacting
on response at other HF bands. One modification
to improve low frequency response is to supplement
the value of C219 (a 0.01 uF capacitor, located
near L88). It is possible to solder a parallel
capacitor to the top side of the RF Unit PCB. Otherwise
the "broadband" circuits in the TS-850 transmit drive
are accepted for what they are. With C219
supplemented in value, 180 kHz output from IF OUT 1
is between about 100 and 250 millivolts,
whereas on HF it is more like 1 volt."
