For those of us with this transceiver, is anyone else noticing the labeled filter widths are wildly inaccurate? Even on FIL1 (.3khz), I have to move up .6khz to escape nearby signals. On FIL2 (.5khz) I have to move .8khz in one direction to accomplish the same. If I’m the only one on the air, this is great but it is proving a little difficult for my new CW ears in crowded conditions, with strong signals even 500hz away coming in so loudly I have to QSY.
Unfortunately I’ve tried four times to ask the folks at Elecraft this question, but they seem to be too busy to get back to me. I just want to know if others are experiencing this as well, or if I have a dud.
I’m guessing they are simple analogue filters? If so they won’t perform anything like as well as the filters in modern SDR radios. Maybe you are expecting rather too much?
“ARCHITECTURE: Superhet with variable-BW crystal filter”
This simple analogue IF filter will have a rather poor shape factor by modern standards and certainly won’t come close to the cliff edges we have become accustomed to with SDR filters.
Unfortunately I left two detailed voicemails after being directed to the tech department that have gone unanswered.
As someone with job spent 50% at a desk, there have been times I was unable to respond to voicemails for extended periods so I can definitely understand the occasional slip between the cracks.
All filters have a shape factor, which is generally considered to be the bandwidth ratio between the -6dB and -60dB points on the curve. The bandwidth is usually quoted at the -6dB points. If the shape factor is 2 (which is good for an analogue filter) then a 300Hz filter at -6dB will be 600Hz wide at -60dB and strong signals will certainly get through.
There is also stop-band attenuation to consider, which mainly comes down to the effectiveness of screening either side of the filter. Ultimately, strong signals will simply bypass the filter if the screening is insufficient. There isn’t a lot of room in the KH1 for good screening!
UPDATE:
Further research reveals that the KH1 filter comprises four crystals (4-node) and a typical shape factor for a 4-node crystal filter is around 4, so a filter marked 300Hz at the -6dB point would be 1.2kHz wide at -60dB, which is pretty well exactly what Joe is observing. I think the KH1 is working to its specification.
You’l have better luck on the Elecraft group on groups.io. Wayne (the company owner) regular comments on it.
** EDIT **
The question has actually been asked in the group previously. Wayne also commented on another thread that a future SW release may allow to adjust the filters.
Joe,
In response to your initial query: Yes, my KH-1 is lousy at rejection of nearby strong signals as much as 3 KHz away. Much worse, in fact, than other small transceivers on the market costing much less.
This rig is useful for a SOTA operator who wants to call CQ and pop out 6 quick contacts from home chasers but frustrating for someone chasing weak s2s.
73!
Mike WB2FUV
Not that I have regrets about my purchase, I do love the rig and feel the benefits outweigh this one downside… but at least I won’t have an issue getting my money back out of it. With how well Elecraft retains value, it’s a cheap rental fee if I ever need to get rid of it.
I have found the filters are ok and some days they work better than other days; eg condx. Re elecraft support, I’ve had pretty good luck with phone and email. For email, I go to Get Support – Elecraft
And fill out form. I usually hear back within 12 hours.
Once on a SOTA summit, I got my KH1 into x it or rit mode and couldn’t change frequency. I panicked a called elecraft and got a tech immediately and he solved my problem. Summit support is great if you can get it.
@K7GUD While my knee is recovering from a pretty good injury, I’ve been activating some parks instead. Today the KH1 did quite well even with the contest on 20m. I found a little carve-out and had 40some contacts in as many minutes, and for a 15 minute window I was averaging 86 Q’s per hour. If there is a gap in the band, the rig is a true joy.
(I was shocked to hear WBN answer my cq, I wondered for a moment if I had accidentally spotted to SOTAWatch somehow).
I really wish I could say the same about my Elecraft CS experience, but we are going on 96 hours without a response to my last email. Honestly worked out fine though, the personal accounts here and on the groups.io link that was posted did an outstanding job of clarifying the matter for me.
Joe. Sorry to hear about ur knee. But glad you got so many QSOs. I’ve had some pretty good pileups with KH1 and it did great. And I was using the elecraft paddle at 24 wpm. I put the magnets in it.
On the weekend, I don’t think they respond to support tickets. Good luck.
I have a KH1 and that’s what I observed with the filters also. I leave it on FIL1 300Hz all the time, with its slack shape its fine as a general use CW filter.
By offering 3 filters and specifying bandwidths, I feel Elecraft are setting expectations beyond what is possible with the simple 4 pole filter. It may have been more realistic to offer “Wide” and “Narrow” filter.
