[JRC] Unblocking the NRD-545

Sun, 27 Jul 2003 20:22:44 -0400

>Chris,
>
>A couple questions on this subject.  First, by wideband converter, do you
>mean frequency extender ? Prior to purchasing my NRD-545, I was told,
>unwittingly, that if you purchased the frequency extender, say in the UK,
>you would have a full coverage system.  Then I found out the configuration
>was actually on the main board itself (Universal Radio bought)
>
>Also, from your email, I postulate that if installing the R13 short on the
>wideband converter (frequency extender ?) This will allow full coverage.
>Therefore: no mods to the main board need be performed based on the
>"parallel" statement.  I wish to perform this mod, as current receiver
>disability is, to me, unacceptable.  I would rather stick needles in my eyes
>than monitor analogue cell calls, both boring and fragmentary.  Took all of
>ten minutes back in 1985.
>
>Thanks in advance for the clarification !

First, a clarification, as Brooke pointed out, there is a typo in the 
first sentence, it should be R24 and R25.

There are two digital inputs to the display board which set one of 
three sets of frequency ranges (see the service manual). 
Interestingly, there are *two* sets of resistors for these inputs, 
one on the main board, one on the wideband converter (extender) 
board, in parallel. The USA setting is with no resistors installed. 
For the full coverage option, you need to short out the RX CHK2 
input. You can do this with either R13 or R25. Shorting out both RX 
CHK 1 (R12 or R24) and RX CHK 2 gives you the "J" option, I presume 
this is Japan. Lots of chunks of UHF are missing, I don't know what 
they are for in Japan. Shorting out RX CHK 1 only is not defined, so 
I don't know what it will do (maybe nothing great, maybe something 
nifty, maybe your radio won't work?)

So much for the FCC reg that radios can't be 'easily' modified for 
cell coverage. I guess soldering one SMD resistor is not defined as 
being easy?

I searched all over the web for mention of this, and found nothing. I 
can't believe I am the first person to discover this. Page 33 of the 
service manual spells out the procedure for setting the coverage, it 
looks like part of the final factory test procedure.

It is curious that there are two places for the resistors. I was 
thinking about the possible combinations, but it doesn't make much 
sense to do it in both places, except making it possible to set the J 
option in two places, so if you change one of them, the other 
overrides and keeps the setting. Weird.

>BTW:  The physical layout of this receiver is awesome.  I use Watkins
>Johnson, Cubic, and IFR systems, and this radio is professionally built,
>except for ONE of the previously noted exceptions of sensitivity, along with
>bandwidth and tuning step limitations at V/UHF.

Yeah, the next step is to see what can be done about that. I've been 
doing head to head comparisons against the Icom R-7000 with the same 
antenna, and, well, there is no comparison. The 545 is a toy. 
Fortunately I bought it for HF, where I really love it compared to my 
Icom R71A.

Anyone want to buy a used R71A ???  ;-)

>Thanks again,
>
>-Scott Schappert
>Molecular Inversion Dynamics
>Engineering Consultant Group, COMSEC
>949.654.0702
>
>
>-----Original Message-----
>From: [email protected] [mailto:[email protected]] On Behalf
>Of Chris Smolinski
>Sent: Sunday, July 27, 2003 2:47 PM
>To: [email protected]
>Subject: [JRC] Unblocking the NRD-545
>
>While scanning through the service manual, I noticed two resistors,
>R24 and R24 on the mainboard. They apparently set the operating range
>for the wideband converter. Default configuration for the US is
>neither installed. Installing R25 apparently opens up the receiver to
>full coverage. In parallel with these resistors are R12 and R13 on
>the wideband converter itself, which are easier to get to.
>
>Installing R13 (zero ohm short) has my 545 tuning everywhere. Not
>that there's much up there to listen to. Plus the sensitivity leaves
>a lot to be desired. I'll be sticking with my Icom R-7000 for VHF and
>UHF reception. Just one of those mods you feel like doing, even if
>you'll never use it ;-)
>
>BTW, I am very impressed with the physical layout and design of the
>inside of the 545. It is much improved over the rats nest of my Icom
>R-71A.
>--
>
>---
>Chris Smolinski
>Black Cat Systems
>http://www.blackcatsystems.com
>_______________________________________________
>JRC mailing list
>[email protected]
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-- 

---
Chris Smolinski
Black Cat Systems
http://www.blackcatsystems.com