| Author |
Message |
    
Sqwirl2001
| | Posted on Sunday, December 15, 2002 - 2:24 pm: | 
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Is there anyway to increase the slide range on the President Grant(first generation with 858 pl chip)? |
Tech808
| | Posted on Sunday, December 15, 2002 - 8:42 pm: |
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Sqwirl2001,
Grant 858 SSB Clarifier Mod:
CUT Banded end of D30
Run a jumper wire from one end of D29 to the other end of D29
Cut Right end of R119 and run a JUMPER from R119 to Banded end of D44.
Trace the purple & white wire from the clarifier to where it connects to the circuit board and cut it loose.
Re-Solder this wire to the circuit board GROUND.
Should give you about 3khz Down and 1khz up of slide.
Not a whole lot to gain from this mod.
Lon
Tech808 |
2600
| | Posted on Sunday, December 15, 2002 - 9:35 pm: |
|
Biggest hassle with making a '858 radio slide wide is that the clarifier leads to THREE different crystals, not just one crystal like the newer radios. The farther you make them slide, the harder it gets to make them line up with each other on the clarifier. Adding chokes, changing varactor diodes and such will cause the middle of the channel to be at one place for AM transmit, and another for AM receive on the clarifier. Not too useful.
73 |
Sqwirl2001
| | Posted on Monday, December 16, 2002 - 9:39 pm: |
|
Thank you both for the information.I already performed the modification but I wanted to see if the range could be increased.I`ll just leave it as is.
73 and Merry Christmas |
Adshar64
| | Posted on Saturday, May 24, 2003 - 7:17 am: |
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858 mods done by adshar64
I have found that is usual for the vco to
stop at 26.085 and exceptional if it gets to 26.065 (done on a Ferris base) even with a superdiode because this is at the lowest
Capacitance in reactance with the vco coil. I tried slug changes etc and nearly got 26.075 stable at one stage (President Washington).
Also slide isn’t easy, 4kc slide is a standard result (standard varactor with no added inductance), I did well to get ~15kc slide and sidebands aligned thx to the good ol superdiodes a Hawaiian guy just sold me recently. I put the standard varactor back in and it reduced
to 7kc slide. These standard 858 varactors slide better than the 8719 stock varactor when replacing those. It’s the 858 xtals that
really let the radio down. They can self oscillate with inductance added, and there are filtering deficiencies in the chassis. However
this one is working a treat. The 9.1v zener replacing D32 is very worthwhile and frequency really came up heaps in this one. I recommend the upslide mod with 2 (usb & lsb)superdiodes with one 5mh inductor (variable if possible to align sidebands) as trimmers Ct4 & Ct5 are removed. AM mode slide as much as the sidebands with the standard varactor, in mine anyhow.
The uhi005 brown vco superdiode mod is probably not worthwhile unless you like listening up high above 28.500. For the keen you remove the whole vco (solder sucker needed, approx 10 pins involved)
On the component (bulges seen in epoxy coat) side you will see a square bulge bigger than the rest. That is the varactor. I used a scalpel to scrape the epoxy away -very carefully little at a time until the legs at the sides (i.e. horizontal) are exposed.
The black square body is removed by carefully using small sidecutters to crush the guts out. The rest can be picked out with a
small screwdriver, leaving the legs exposed. Superdiode is soldered to these with the band on the right side.
Resolder to pcb and you are ready to go. L17 slug will tune lower in
the can on the vco coil. There are different places in the slug range
where it will lock but only one position is comprehensive and reliable. Some playing around is required here to find it. Coming up
from bottom of can until lock is found and checking frequency ends with small fine tuning worked for me. Get 26.085 - 29.895.
power and receive drop off quickly about 1 MHz from centre tuning.
L37 broadband mod (coil tap changes) is required. |
Adshar64
| | Posted on Saturday, May 24, 2003 - 7:27 am: |
|
A few notes on a 858 Washington clarifier setup in addition to previous post.
After basic mod, I fitted superdiodes to the usb
and lsb varactor circuits, fitted a 9.1 v zener diode replacing d32
and had some inductors added to the superdiodes.The 858 downmixer
crystals dont seem to slide real well in this one and had problems
getting a 10 kc drop with lsb-usb alignment as well, so mode change
doesnt require clarifier adjustment. Anyhow the way it seemed to go
up more than down I ended up setting it up for a 10 kc upslide
instead and also i had removed the parallel xtal trimmers to get the
range I wanted. I set up the clarifier knob on the shaft at 12.00
aclock at centre so the clockwise travel was way more than the
anticlockwise.I played with different varactor values in the usb &
lsb varactors, until I had the aligned usb - lsb 1khz tone freq ie
on ch35 ie: 27.354 lsb and 27.356 usb at the 12.00 oclock pos I
originally set the lsb to.
The trick to the exact alignment as i had no trimmers now, was to
carefully slide the end usb varactor inductor wire turns off the
former(reducing inductance) to close a 20hz difference I had .
anyhow worked a treat in the end.
These xtals can self oscillate with too much varactor inductance
added (as happened to me)esp on lsb with a audible recieve tweet on
the low end of the clarifier range, this can be tuned out with a
5kohm pot in the clarifier control ground connection(or get xtals
cut).
Anyhow that was my experience with this |
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