[Premium-Rx] Receivers

[Michael O'Beirne]

Dear Charles,

I agree with your analysis of the bugbears of tuning.  The best solution I 
have encountered is variable rate tuning.  That can give its own problems 
depending on how much speed up is achieved and at what "rev points".   I 
recall in a WJ-8888 there is a big acceleration factor but for some reason 
in the one I looked at it has a "flywheel effect" - when you stop turning 
the knob the tuning still kept going.  You then reverse the tuning and 
encounter overshoot the other way.  Drives you completely nuts.  It's a bit 
like "bracketing" in directing artillery gunfire, if you know how that works 
(it's very noisy!)

In the Icom R71-E the speed-up is only about x2.  The speed-up with the 
Racal RA3701 for example is vastly greater and very comfortable to use, 
thanks no doubt to having far sophsticated software.

I must say in some ways the old "Collins-type" double-conversion system with 
a stable analogue VFO tuning around 10 kHz per rev at a constant rate had a 
lot going for it.  Perhaps I'm just an old fogey.

As for cycling round and round with a one-way button system - that too 
drives me nuts.  Some of us of a certain age may remember dedicated rotary 
controls called "SELECTIVITY", "AGC", BAND", "NOISE LIMITER", "AERIAL 
ATTENUATOR" and the like.  You did not need a huge manual in front of you to 
make some sense of an over-cluttered front panel.  Bring back the RA1772.  I 
like big lumpy bits of kit, albeit it is probably a big no-no to say that on 
this site.

The main reason for these push buttons on professional gear is because they 
are all designed for remote control for use by professional listeners such 
as NSA and GCHQ.  Their receivers and aerials are sited in some distant 
quiet field where the local QRM is minimal, and the remote end of the 
receiver (basically a glorified modem) is located in a comfy office building 
miles away in Washington or London etc.

Simulating a two-state on-off push button in a digital format to create a 
data stream via a modem is easy.  But trying to simulate a multipole rotary 
switch digitally is presumably horrendous.

Hence there are lots of on-off push button switches.

In any event I bet an on-off switch is vastly cheaper than a good quality 
rotary switch, and doesn't call for a skilled technician to have to hand 
solder all the many wire connections to the switch wafers.

An exception to the cost may be the excellent top quality push buttons that 
you can see on some radios eg the RA3701 / 3791.  I think they were made in 
Switzerland.  They certainly have a nice long push and feel good.  In 
contrast, I was not much taken by the quality of the buttons on the HF-1000. 
I am sure their owners love them, but just think how much better they could 
have been had they not been designed to a tight budget and had retained the 
build quality of their older brothers.  Allowing for inflation, the cost of 
a RA1772 in 1974 would be the equivalent of at least three HF-1000s and 
possibly more.

73s
Michael
G8MOB


----- Original Message ----- 
From: "Charles Steinmetz" <csteinmetz at yandex.com>
To: "PremiumRX" <premium-rx at mailman.qth.net>
Sent: Wednesday, January 01, 2014 11:27 PM
Subject: Re: [Premium-Rx] Receivers


> Michael wrote:
>
>>The TenTec 340   *   *   *  manual tuning is very slow.  It's more of a 
>>fine tune rather than for swift navigation.
>
> Like many, many radios, the RX340 manual (knob) tuning follows the UP/DOWN 
> STEP (keypad) tuning interval.  That is, each count of the rotary encoder 
> changes the frequency by whatever amount is set for the STEP control (a 
> range of selections from 1Hz to 1MHz).  So, the manual tuning can be very 
> slow to insanely fast depending on the STEP setting.  I find the 50Hz step 
> position to be about right for manual tuning on the RX340.  The JRC 
> NRD-545, Harris RF-590, WJ 8711, and many, many other receivers all act 
> this same way, with some slight variations.
>
> Personally, I find this a particularly useless arrangement.  I usually 
> want the UP/DOWN (keypad) tuning steps to be the same as the band 
> channelization (generally 5, 9, or 10 kHz on the MW/SW bands, sometimes 
> higher at VHF/UHF), but at the same time I want the knob tuning to be 
> much, much slower -- a good rate for scanning and fine tuning.  The Drake 
> R8B is the only premium receiver I'm aware of that allows this.  Its 
> tuning knob always tunes at a good band-scanning/fine tuning rate, and its 
> UP/DOWN (keypad) tuning varies according to the band channelization.  (The 
> Drake SW-8 also works this way.)
>
> The RX340 also has some strange limitations, due (I suspect) to 
> insufficient DSP horsepower.  The notch filter is unavailable in AM, SAM, 
> ISB, and at BWs above 4kHz in LSB/USB.  The PBT is unavailable in SAM and 
> ISB.  The BW is limited to 4kHz and above in SAM, and is not adjustable at 
> all in ISB.  Ergonomically, you have to cycle stepwise through the modes 
> and tuning steps, and it uses one control to adjust BW, BFO, PBT, notch, 
> AGC, squelch, and noise blanker.  The WJ 8711/HF1000 has similar quirks.
>
> Best regards,
>
> Charles