I have just finished putting together, and testing a 6m preamp kit from Down East Microwave. As I use the RX Ant input on the lower bands, and not wanting to put in a relay, I have made up a Diplexer to separate out the 2 signal paths.
Although the arrangement is a bit of a lash up it has proved the concept, and it's worth during a short 6m opening the other evening. Without the preamp I noticed no discernible different in the K3 noise level when connecting the antenna. With the preamp I get about an S2-3 indication. More importantly signals which were there but not readable, with the preamp they gave 100% copy. I think that my present preamp gain at around 22dB is a little excessive, so I will drop it back to about 15dB or so. Before I get swamped with requests etc, I should stress that my arrangement is not really reproducible, and you should wait until Elecraft releases their preamp solution. Y.M.M.V 73 Stewart G3RXQ On Thu, 3 Jul 2008 08:50:03 +0100, Ian White GM3SEK wrote: > On Tuesday, Dick K5AND wrote: > >> Ciao, from CY0X, Sable Island..... > [...] > >> Since it is so easy to switch out the outboard preamp, we have frequently >> done this on some of the weak sigs just to see if we could still hear them. >> In many cases we could hear them Q5 with just the internal preamp. Ian, >> GM3SEK, et al, have pointed out that the stock radio NF is somewhere in the >> 8-10db range, which is not stellar as six meter radio specs go. Nonetheless, >> you'd be surprised at how many weak sigs we can still hear with only the >> internal preamp engaged. >> > That's not surprising at all, as the K3 is only slightly lacking in > sensitivity on 6m. But contrary to other reports from users in very > quiet sites, my stock K3 can NOT hear background noise at 50MHz. > > Before making that statement, I took a couple of days to confirm that > nothing else is wrong with the system. Receiver sensitivity meets > Elecraft's 'typical' specification with a few dB to spare. Feeder loss > was re-measured. And above all, I re-confirmed that my old IC-746 CAN > hear background noise from the same antenna/feedline with a comfortable > 3-5dB margin. > > A good operator like Dick can often make up for a few dB lacking in > signal/noise ratio... but only at the expense of greater operator > fatigue, and with the knowledge that some marginal QSOs *will* be lost, > when a more sensitive receiver could have pulled them through. That is > precisely why the receiver at CY0X has a prototype Elecraft preamp. > > One small correction: Elecraft's specification for a typical MDS (noise > floor) of -136dBm in a noise bandwidth of 500Hz corresponds to a noise > figure of about 13dB (significantly more than 8-10dB). Cutting through > the technicalities, at a genuinely quiet 6m site that deficit *is* > noticeable - a gap in the K3's otherwise all-round excellence. _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
