ORIGINAL: hellcat 1
The second IF on both radios is 455KHZ but I dont't know about the first IF freq. They use commerical IF transformers and filters and what is available is 10.7MHZ and 10.9MHZ> That would be where the difference could be. You should see another crystal that would be 455MHZ above or below the other freqs. All dual conversions receivers have at least two crystals and some have two crystal filers in them. That's what you are looking at that says w55h. It's a 455Mhz filter.
Thanks for clarifications. I have put Electron 6 together and
installed into my son's electric trainer while pulled out the
original Hitec HFD-08RD (aka RCD3500). In between we took close up
pictures of the both, from both sides. The circuits look similar, yet the
standard-size RCD3500 has two obvious quartz crystals build in
(besides the removable one). It seems to me Electron 6, the micro, had
only one such crystal, but I could not read its frequency.
The two crystals of RCD3500 are for 10.7MHz and 11.155MHz. Hence
apparently the first IF is 10.7MHz and the second is the difference of
the two, 455kHz. I wonder how a (quartz) crystal, even on 10MHz can
pass 20 or even 10KHz bandwidth, I thought true quartz crystals have Q
in the range of at least 100000; well, they probably can make them
If Electron 6 does not have a counterpart of its bigger brother's
pass-through crystal on the first IF then they probably are not quite
the same in their fidelity as marketed by the manufacturer.
How to understand the filter's nature by the marks on them? Do W, H
and T mean something specific?
I have a GWS-for-Futaba DC RX crystal on channel 22 with me, and hope
to check which precisely frequency it oscillates on in the
receiver. This can be compared with the same for the genuine Hitec one
at channel 19 and 33 or 40 I have at hand. This will give a final answer to
the compatibility issue.
By the way, last May I got a reply from Steve Morton at Hitec/Multiplex
Customer Service -- it said the measured frequency for the TX on
channel 20 must be approximately 72.191MHz. Does this make sense if
the frequency for this channels is nominally 72.190MHz and Hitec employs
NEGATIVE shift? Since that time I am trying to find out what, after
all, is the precise carrier frequency and the maximal deviation,
nobody answers as if it were the top secret!
The RF part seems to have three identical coils and one which visually
differs, lower and with differently looking/colored core screw. I
guess the three similar are preselector LC filters. Do you
know what is this fourth one -- is it an image frequency killer, or an
inductance for the first heterodyne, or has something to the second