Receivers

[Andre' Kesteloot]

Alan Melia wrote:

> Hi Vaino, I can confirm your findings on the AOR 7030+ . I have been using
> one since March and I have found it just as good as you do. I also have a
> HF150 and have tried a Palomar LF to 3.5MHz converter. To dispose of the
> easy one first, the Palomar is not worth any consideration except possible
> for BC listening, despite being used in front of a good HF transceiver with
> 300Hz CW filters.
>
> The HF150 was much better than I would have expected. It is let down for
> serious work by a poor shape factor on the SSB filter (it is not available
> with a cw filter) Tuned to 138.05kHz the signal from DCF39 is not far
> enought down the skirt (-60dB) and gives a trace on the waterfall display.
> Its strong signal handling seems to be quite good ( I have a 1KW MF BC
> station about 2 miles away and 500KW BBC World Service TX site about 10
> miles away) It may be worth grafting a cw filter into it after the SSB
> filter, and maybe cascading another SSB filter to improve the shape. If you
> remove the battery carriers there is plenty of room for some daughter pcbs.
>
> I bought the 7030+ as the first new bit if kit I've bought for about 12
> years ( I am fairly stingy) impressed by the specification on strong signal
> handling which I have suffered with the Kenwood R1000 , FRG7700/8800 and a
> lot of the kit of that vintage. These are particularly useless as they put
> in a 20dB attenuator below 2MHz! I must say in operation the 7030 lives up
> to all its claims, and I think it holds the record as the only bit of kit
> that has lasted 6 months in my shack without being 'modified' or 'improved'
> (I don't count fitting the Collins 500Hz filter) The facility I like most is
> the pass-band-tuning. I select LSB and put the 'carrier' on 138.10KHz (yes
> it has got 10Hz resolution) and  I use the 2.4kHz filter to display band
> activity on FFTDSP4. The pass-band tuning is stored as a function of the
> MODE so I can pre-programme the 500Hz filter to interesting parts of the
> band and drop it over a signal very quickly using the mode change button.
> Thus on LSB mode (with the 500Hz filter selected) with a -200HZ offset I get
> the QRS end of the band, on the CW position with about -1.3kHz offset I get
> the centre of hand-keyed activity at 136.5, and the data mode can be tuned
> to another area. Ok reading 1.5kHz tone CW is not optimum, but with a quick
> button toggle I can tune the BFO to bring the tone down whilst not losing
> the signal. This is maybe a bit fiddly when compared with transceive (I was
> brought up on 'separates' when I got my ticket!) but it must be a listeners
> dream (It certainly fulfills this listeners dreams) I haven't managed to
> prise it off the aerial yet to do much in the way of measurements on it, and
> my TF2002 sig gen has gone sick. I used a Farnell DSG1 synth audio gen and
> an attenuator to try to measure the input terminal voltage of stations I am
> seeing and copying on the waterfall. The problem with this is that it is not
> intended for low level measurements and has a lot of signal leaking out on
> the coax screen. The following tests were done at 73.00kHz.  The lowest
> reliable signal I could apply was 0.1uV which gave 22dB S/N on FFTDSP (no
> aerial noise of course) I estimate that I can copy cw at 20nV and probably
> read QRS at 5nV. These may not be sensible levels....but it indicates why I
> am hearing reasonable distances with a fairly useless antenna ( 16t loop
> with Q of approx 15 !) This was using the internal preamp, and the dynamic
> range is about 95dB at the frequency in this state. (It uses DDS generation
> for the local oscillator to keep the reciprocal mixing noise down) Only
> strong lightening crashes seem to reach this level on my aerial.  Stereo
> audio output (from before the Vol control) with separate level and tone
> controls (in software) allow you to feed the computer and audio processing,
> or as I do run FFTDSP on one PC and Spectrogram on another. There is also a
> 20mV output at the IF (455kHz) available on the accessory socket. There is a
> mod (official) to give an analogue S-meter output voltage (not linearised by
> the processor as is the dispay bar graph)
>
> On the hum problem there are separate RF and DC grounds. I have the dc
> supply cable wound round an old TV line-output ferrite. It is possible that
> grounding the negative side of this dc supply would help. I find it is
> possible to couple in hum via the coax screen if you do not use an RF
> ground. This is achieved by putting the ground terminal of the wire-aerial
> input to a good RF ground. It make a lot of difference. Also make sure your
> PC case is well grounded. I had one with a faulty 'earth' wire and could get
> a tingle between the outers of the phono audio leads to the sound card and
> the lead from the accessory plug of the radio.
>
> All I can say is that if there are comedians trading in the earlier 7030 for
> the 'plus' and there are good priced 2nd hand versions available, you will
> have to pay a LOT more money to get a better receiver. The 'plus' only has
> audio notch, more memories and a few other trimmings There is all the info
> on the AOR web site to do the upgrade (a lot is software) which is well
> within the capabilities of a confirmed 'Lowfer',and the basic performance is
> just as good. I'm now looking for a narrower CW filter I can 'bodge'in as
> there is a spare position (it will take 7 IF filters at 455kHz, it comes
> with 5 fitted) I guess I might have to make this myself. I have played with
> ceramic resonators but without success so far.
> What more can I say ( Oh yes, its designed and manufactured in England not
> Japan)  I'm hooked !!
>
> I hope to be able to borrow a Lowe HF225 to compare soon (Watch this space)
>
> I hope that lot is interesting and maybe useful. It is an expensive bit of
> kit for 'just' a receiver, but I have not heard anyone else except Vaino
> mention it in the LF context. His enthusiastic endorsement proded me to put
> down my findings.
>
> 73 de Alan G3NYK
> Alan.Melia@btinternet.com