K2 ATU question
Locked
 
|
I've recently build my K2 (serial 4377) which works great, and I'm very happy with it. Unfortunately, I can only use indoor or very small outdoor antennas, so I'm currently experimenting with mag loops. While doing so, I noticed that ATU use becomes very inconvenient. This is my scenario: I'm using an indoor wire antenna for all bands except 30m, where I'm testing a home built mag loop. The wire antenna is connected to ant #1, the mag loop to ant #2. The mag loop is resonant and doesn't use the ATU, while the wire antenna needs the ATU. Now each time, I change to 30m, I do have to disable the ATU manually by switching it into CALS mode, which is very inconvenient. Alternatively, I can connect a dummy load, tune the ATU into the dummy load on 30m, and then reconnect the mag loop. The problem with this second approach is that after accidently tapping tune, I will have to repeat the whole process (disconnect antenna, connect the dummy load, ...). Since the given setup (having a resonant antenna and another one that needs the ATU) seems pretty common to me, I do assume that there is a simpler solution. Is it possible to disable the ATU for one of both antenna connectors, or for a specific band? Any other trick to make changing bands simpler? Regards Uz -- Ullrich von Bassewitz [hidden email] _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
|
|
G'day,
> I'm using an indoor wire antenna for all bands except 30m, where I'm testing a > home built mag loop. The wire antenna is connected to ant #1, the mag loop to > ant #2. The mag loop is resonant and doesn't use the ATU, while the wire > antenna needs the ATU. > Now each time, I change to 30m, I do have to disable the ATU manually by > switching it into CALS mode, which is very inconvenient. Alternatively, I can > connect a dummy load, tune the ATU into the dummy load on 30m, and then > reconnect the mag loop. The problem with this second approach is that after > accidently tapping tune, I will have to repeat the whole process (disconnect > antenna, connect the dummy load, ...). > > Since the given setup (having a resonant antenna and another one that needs > the ATU) seems pretty common to me, I do assume that there is a simpler > solution. Is it possible to disable the ATU for one of both antenna > connectors, or for a specific band? Any other trick to make changing bands > simpler? Can't see the problem. I have a log periodic for 18-30MHz on ant-1 and a vertical for lower bands on ant-2. It does not matter if the atu stays in circuit and "tunes" the matched resonant antenna. Just the same as matching to the dummy load. My vertical is a good 50 ohm match on 10MHz but I also very occasionally press it into service on 7MHz where the ATU keeps the PA happy. Regards, Mike VP8NO _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
|
|
Hi Mike,
> Can't see the problem. I have a log periodic for 18-30MHz on ant-1 and a > vertical for lower bands on ant-2. It does not matter if the atu stays in > circuit and "tunes" the matched resonant antenna. Just the same as > matching to the dummy load. My vertical is a good 50 ohm match on 10MHz > but I also very occasionally press it into service on 7MHz where the ATU > keeps the PA happy. What you described is correct. However, a magnetic loop or other narrow-band antenna that needs to be tuned to frequency should be run without an auto-tuner in the transmitter. When an auto-tuner is engaged it is nearly impossible to tune the loop correctly to resonance resulting in troublesome matches that can stress both the loop antenna and tuner components. I use magnetic loops with other transceivers that allow the tuner to be disabled, but not with a K2. My K2 is used with numerous wire dipoles, full-sized loops, an LPDA, and verticals, but not with magnetic loops. Gus Hansen Email: [hidden email] ..................... If you think no one cares that you are alive try missing a couple of loan payments. _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
|
|
In reply to this post by Mike Harris-9
On Tue, Sep 14, 2004 at 11:23:18AM -0300, Michael Harris wrote: > Can't see the problem. I have a log periodic for 18-30MHz on ant-1 and a > vertical for lower bands on ant-2. It does not matter if the atu stays in > circuit and "tunes" the matched resonant antenna. Just the same as > matching to the dummy load. My vertical is a good 50 ohm match on 10MHz > but I also very occasionally press it into service on 7MHz where the ATU > keeps the PA happy. Unfortunately, it's not that easy. Matching a combined feeder/antenna system with a tuner so that the PA sees 50 ohms doesn't mean that the antenna is actually working. What you say is true, provided that the antenna is resonant, and has 50 ohms with no imaginary part. But if you don't know that for sure, for example if you're experimenting, or because the antenna has a very low bandwidth (see below), just matching it with the ATU won't help. A mag loop is special, because it has a very narrow bandwidth (often 10khz or less), so changing frequency means retuning the antenna. But to tune the antenna, one needs to know the real SWR. And this is the point where the ATU needs to be switched off, because it will just correct the SWR as far as the PA is concerned, but it will not make the antenna resonant. Regards Uz -- Ullrich von Bassewitz [hidden email] _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
|
|
In message <[hidden email]>, Ullrich von
Bassewitz <[hidden email]> writes Surely this doesn't matter. Once the ATU in the K2 has been tuned once, then it won't attempt to correct for any mismatch (caused by tuning the mag loop) until you press the tune button again. Trev G3ZYY >Unfortunately, it's not that easy. Matching a combined feeder/antenna system >with a tuner so that the PA sees 50 ohms doesn't mean that the antenna is >actually working. What you say is true, provided that the antenna is resonant, >and has 50 ohms with no imaginary part. But if you don't know that for sure, >for example if you're experimenting, or because the antenna has a very low >bandwidth (see below), just matching it with the ATU won't help. > >A mag loop is special, because it has a very narrow bandwidth (often 10khz or >less), so changing frequency means retuning the antenna. But to tune the >antenna, one needs to know the real SWR. And this is the point where the ATU >needs to be switched off, because it will just correct the SWR as far as the >PA is concerned, but it will not make the antenna resonant. > >Regards > > > Uz > > -- Trevor Day SIP: [hidden email] _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
«
Return to Elecraft
|
1 view|%1 views
| Free forum by Nabble | Edit this page |