XV144

[Wyn Hughes]

I recently completed construction and alignment and test of the XV144. I encountered no real problems with the build. I've had it running with my IC-781 as an IF for a couple of weeks. I have a couple of questions and some comments:

(a) While installing the RF module and the heat spreader, on the bottom cover, using the procedure described on page 48 of the assembly manual, I noticed that by holding up the finished bottom cover assembly close up to a bright light, a very very thin sliver of light could be seen creeping through between the heat spreader and the lower thermal conduction pad and the bottom cover at the midway point of the PF power module . No amount of extra screw tightning or even pressing the parts involved in the middle of the RF power module, as gingerly as I dared, would prevent that tinly flicker of light from getting through. There is certainly no lack of heat transfer to the bottom cover, which warms up across a wide area (positively flushes in fact) as soon as maximum permitted power is applied to the PA. The area also cools quickly when going to receive. However I'm wondering how the light was getting through - could it possibly be slight out-of-toerances in the heat spreader or bottom cover?

(b) Receive gain of the XV144/IC-781 combination seems to be very high. Even with the preamp on on 28 Mhz with an antenna connected, the IC-781 is very quiet in terms of phase noise, there being no visible 'grass' on the spectrum scope visible either, even with the antenna connected. When the XV144 is brought in line there is an audible increase in background noise on 144Mhz and the 'grass' is clearly visible on the spectrum scope, even with the preamp on the IC-781 switched off. I have taken to using 10db of attenuation in the RF stage of the IC-781 to counteract this effect, although I suspect it would be better if the gain of the XV144 could be reduced. Any ideas?

Some general onservations - build time in my case, admittedly rather ponderous, was around 25 hours. I bought an anti static mat for this XV144 build having read other reports that suggested some of the components are particularly sensitive to ESD. I also bought and installed the crystal oven and the extra tilt bail stand. The stand is quite useful, as it enablea a small fan to be placed on the bench beneath the vent holes in the bottom cover, to blow air into the enclosure and hopefully out of the top cover! Does away with the need for whacking the panels.

I noticed a couple of manual inconsistencies. Mine came with Rev B March 2006 and Rev B-1 August 2006 Errata in the case of the Assembly Manual, and Rev C April 2006 and Rev C-1 May 2006 in the case of the Owner's Manual. The download link on the website in the case of the Errata to the Owner's Manual takes you to a previous version of the Errata (B-1, I think although the website refers to the later Errata but does not take you there). The Rev C-1 Errata to the Owner's Manual does, among other things, address the 'L17 tuning sug' issue that was recently being discussed here. I suspect there are also a couple of typos in the Assembly Manual, page 40: last step left hand side refers to installing a jumper in the lower left quadrant (think it should be right); and same page, right hand side last step, refers to installing Q1 in the lower left quadrant (think it should be right).

All in all a very nice - and to me at least - very sophisticated piece of equipment. Not cheap but just a neat and clever way of getting on to 2 metres all mode with a high performance outcome. The LEDs and finish are really great to look at. The brightly lit XV144 makes my ex-K2 seem rather dowdy in comparison. Unfortunately I can't see the moon very often at all from my surrounded high rise apartment, otherwise I'd be tempted to try some EME.

73
Wyn, VR2AX
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