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Test-Berichte
Zeitschrift "Funk"
Ausgabe 5 / 2001
Verlag Technik und Handwerk GmbH
Internet: www.vth.deWeltempfänger-Testbuch Nr.10
Autor Nils Schiffhauer
Erschienen im Siebel Verlag
Internet: www.siebel-verlag.de
Nachfolgend ein Auszug aus einem Test-Bericht des Shortwave Magazine,
der vollständige Artikel ist direkt über den Verlag zu beziehen.
SEE SHORTWAVE MAGAZINE FOR PICTURES AND FULL DETAILS.
The Fairhaven RD500 A Second Look At An Intriguing Receiver
Having already reviewed the RD500 receiver last year, John Wilson was pleased when Fairhaven offered a second look following revisions to the original receiver. How could he refuse? Although still called the RD500, there have been some real changes to the unit, the first being a decided upgrade in the external appearance. The finish on the case, and the addition of a neat styling touch in having the name Fairhaven incorporated on the top cover make the RD500 much more attractive to look at, and whilst I appreciate that this doesn’t help the performance of a receiver, it does show that the makers are listening to what their customers are saying and actually doing something about it. More interesting to me was the change of first IF filter frequency and the upgrading of the filter specification to take account of my original observations about the non symmetrical nature of the i.f. response and the effect this had on the signal handling capabilities of the receiver.
It Ain't Heavy - Its just Heavier
When I picked up the RD500 I realised that this was heavier than I remembered and was impressed by the two N-type professional antenna connectors on the rear panel in addition to the original pair of SO-239 connectors, which you may recall were for connection of either a low impedance coaxial fed antenna for the l.f./m.f./h.f. ranges or a whip antenna at a higher impedance. You may also remember the clever use of both connectors at the same time to provide r.f. noise cancelling facilities. The two new connectors were labelled "48 to 860MHz" and "860 to 1750MHz" so here was something exciting, because I hadn’t expected the test receiver to come equipped with this amazing frequency coverage. And amazing it is when you consider how compact the RD500 seems in comparison to other receivers, even those which do a great deal less than the Fairhaven. Since the v.h.f. and u.h.f. coverage were the most important additions since my first review, let’s start with how the receiver performed up there in the wide open spaces. I had an immediate problem in that my Rohde & Schwarz SMY generator stops at 1040MHz so I couldn’t carry out sensitivity measurements above that frequency. However, with a measured sensitivity at 1040MHz on narrow f.m. of - 118dBm for 12dB SINAD, the receiver was clearly pretty hot, so I carried on down as shown in Table 1. The sensitivity was measured in dBm for 12dB SINAD with 3kHz deviation at 1kHz for f.m, the RD500 set to 'FMN', and with 60% modulation at 1kHz in a.m., with the RD500 set to 'AMN'. The receiver r.f. preamplifier was switched on during the tests. I encountered a gap between 590 and 670MHz where the receiver synthesiser was apparently not working.
590 to 670MHz is now catered for in all modes......C.B.
Hot Little Receiver
As one of my colleagues from Exeter University often says to me "What’s that in real microvolts?", and to give you some idea of the level of signals you will hear, -117dBm is equivalent to 0.3µV p.d. and that makes the RD500 a hot little receiver. Connected to a small log periodic I could hear signals over really long distance, and had the experience of tuning around during a sporadic-E opening when the band between 50 and 80MHz was simply awash with broadcast and TV signals from Italy to the Baltic States. Mind you, the same opening meant that I couldn’t carry out any EMC measurements on the open area test site, but that’s another story. Great fun. For those who may want to tune s.s.b. signals at v.h.f., I did find that the demodulated signal became more 'wobbly' as I tuned higher in frequency, which I put down to noise from the synthesiser, but on the 144MHz and 432MHz amateur bands there were no problems. I wouldn’t however recommend trying to listen to s.s.b. or c.w. on 1296MHz - but who does? I suppose that may trigger a letter from a keen v.h.f. contest operator but I’ll take a chance. I did encounter one barnstorming internal spurious carrier on 600MHz, but that’s the only one I fell over. I didn’t have the time to tune the entire 1700MHz range in 100Hz steps, so if you find another sproggie, I’m sorry I missed it. Overall, I couldn’t fail to be impressed by the performance of the RD500, and I find it hard to guess how it all fits in that tiny box.
Synthesiser performance has been tweaked at UHF, since the prototype was sent out for review. We had hoped to send a later version to John but the magazine deadline prevented it. As with any receiver a few sproggies exist and if you spend a day or two tuning the whole 1.75 gigs in 5Hz steps you will find a few, the important thing is that sproggies are kept away from amateur bands and away from 12.5kHz steps, so you can tune for miles without experiencing problems. ......C.B.
Symmetry
Since the first i.f. filtering had been changed, I went back and re-measured the 3rd order intercept point at h.f. and found that the response was now symmetrical with a figure of +10dBm easily attained at 20kHz spacing, just as the handbook says. I also found that operating the RD500 became very easy once I had mastered the triple function keypad, and I do prefer this approach to the Zen simple layered menu system, even though that is ultimately more flexible and extendible. The RD500 keypad in particular can be a mite confusing when you have a single key labelled as 'A', '2', and 'BP FILT' or 'W', '9', 'CLK'. Despite the obvious increase in cost, it would have been better to engrave the key tops with the numbers so that they were unmistakable, and had the second and third functions on the panel alongside. Don’t get the idea that operation is very difficult, it isn’t, but at first encounter you have to be very careful in determining which key is which. Having said that, it’s a delight to have all the receiver functions available right there on the panel, even with second and third functions, but if I had been in a position to influence the design of the RD500 I would have insisted on a larger front panel in the first place so that all the controls could have had greater spacing between them. Going one step further, and suggesting the ultimate heresy to those who like micro styled receivers, if the RD500 was the same size and shape as, say an Icom receiver or the NRD-545, it would be an absolute stunner. But to go back to the keypad; Fairhaven can provide a small laptop type of keyboard which will plug into the PC interface socket on the rear panel, and this enables easy entry of data in a more familiar format. I haven’t had the opportunity to try out the Windows based software from Fairhaven, but this would probably fulfil all needs for easy operation of the receiver, as well as great flexibility in entering database details. It’s worth mentioning that with two megabytes of memory fitted, you can store simply huge amounts of information and use it to drive the receiver. Imagine having the whole of Passport to World Band Radio or the Klingenfuss Guide right there in the receiver...what power.
It's British
As far as the million other functions and features which embellish the RD500 are concerned, I suggest that you go back to my original review rather than have the pages of the magazine filled with the same information this time around. All I can say is that I was impressed with the RD500 at our first meeting, and I’m even more impressed now. This is really innovative design and deserves success. I know of no other receiver which combines all the features found in the RD500, and this, coupled with the very wide frequency coverage makes the RD500 a very tempting prospect for anyone looking for a single receiver to use as an entire listening system. And it’s British, so there are people here who do things other than spray beer over Belgian football fans and kick policemen unconscious.
Thanks again go to Clive Buxton at Fairhaven for supplying the review receiver. If you missed John's first look at the RD500, don't despair, back issues are available from the SWM Book Store at £2.75 each. - Ed.
Table 1:
MHz FM(N) AM(N)
1040 -118 -112
940 -116 -111
840 -118 -113
740 -118.5 -114
540 -120 -116
440 -122 -118
340 -123 -120
240 -122 -119
140 -123 -119
80 -121 -117
50 -119 -115.5
(The VX model includes video o/p and stereo FM)
PW Publishing Ltd. Short Wave Magazine & Practical Wireless.
The Home of British Hobby Radio. Editorial: Tel: +44 (0)1202 659910
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