BCB sensitivity
Locked
 
|
Mike,
How do you tune the ATU optimally for BCB, since you can't transmit? Windy KM5Q > Sometimes the ATU helps and sometimes the ATU hurts signals on the > BCB. _______________________________________________ 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 |
|
|
You can set the KAT3 menu config entry to LCSet. Exit the menu then
tap ATU TUNE. You can set the L and C values individually with the A and B VFO controls. But it doesn't seem to make any difference in the AM received signal as far as I can tell. I'm using a 100' wire for an antenna. 73, Drew AF2Z On Fri, 18 Jul 2008 22:53:52 -0600, KM5Q wrote: >Mike, > >How do you tune the ATU optimally for BCB, since you can't transmit? > >Windy KM5Q > >> Sometimes the ATU helps and sometimes the ATU hurts signals on the >> BCB. _______________________________________________ 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 |
|
|
Also, while dialing in the L and C values, tap ANT to switch between
CA and CT. However, it seems you can't adjust the two caps independently; whatever value is dialed in for CA is duplicated for CT, and vice versa. Is this a bug? 73, Drew AF2Z On Sat, 19 Jul 2008 08:16:37 -0400, AF2Z wrote: >You can set the KAT3 menu config entry to LCSet. Exit the menu then >tap ATU TUNE. You can set the L and C values individually with the A >and B VFO controls. But it doesn't seem to make any difference in the >AM received signal as far as I can tell. I'm using a 100' wire for an >antenna. > >73, >Drew >AF2Z > > _______________________________________________ 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 |
|
|
Ok..., it seems the ANT switch, which is supposed to be switching
between CA and CT while in the LCSet mode, is actually switching antennas as it would do in normal operation. I guess this is a bug, unless I'm doing something wrong here... 73, Drew AF2Z On Sat, 19 Jul 2008 08:30:44 -0400, AF2Z wrote: >Also, while dialing in the L and C values, tap ANT to switch between >CA and CT. However, it seems you can't adjust the two caps >independently; whatever value is dialed in for CA is duplicated for >CT, and vice versa. Is this a bug? > >73, >Drew >AF2Z > > >On Sat, 19 Jul 2008 08:16:37 -0400, AF2Z wrote: > >>You can set the KAT3 menu config entry to LCSet. Exit the menu then >>tap ATU TUNE. You can set the L and C values individually with the A >>and B VFO controls. But it doesn't seem to make any difference in the >>AM received signal as far as I can tell. I'm using a 100' wire for an >>antenna. >> >>73, >>Drew >>AF2Z >> >> > _______________________________________________ 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 |
|
|
Ok, my final conclusion (i promise)....
Manually adjusting the L and C values of the ATU DOES have an effect on BCB reception (had my RF gain turned down before, so seemed like there was no difference). Maximum L (17.35 pH) gives maximum received signal strength on a short antenna, as expected. However, you can't adjust CA and CT independently. And checking all of my pretuned bands the values for CA and CT on any given band are equivalent (which seems odd). Furthermore, merely selecting between CA and CT with the ANT button while in LCSet mode has an effect on the received signal-- a couple of s-units difference between the two is what I noticed. (But I don't think it is the antenna relay being switched, as mentioned before.) What I want to know is, are the displayed values for CA and CT correct, and can they be adjusted independently of each other? BTW, I am using F/W ver 2.13. Thanks, 73, Drew AF2Z On Sat, 19 Jul 2008 08:43:44 -0400, AF2Z wrote: >Ok..., it seems the ANT switch, which is supposed to be switching >between CA and CT while in the LCSet mode, is actually switching >antennas as it would do in normal operation. I guess this is a bug, >unless I'm doing something wrong here... > >73, >Drew >AF2Z > > _______________________________________________ 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 |
|
|
[hidden email] wrote:
> Manually adjusting the L and C values of the ATU DOES have an effect > on BCB reception (had my RF gain turned down before, so seemed like > there was no difference). Maximum L (17.35 pH) gives maximum received > signal strength on a short antenna, as expected. > However, you can't adjust CA and CT independently. And checking all of > my pretuned bands the values for CA and CT on any given band are > equivalent (which seems odd). Furthermore, merely selecting between CA > and CT with the ANT button while in LCSet mode has an effect on the > received signal-- a couple of s-units difference between the two is > what I noticed. (But I don't think it is the antenna relay being > switched, as mentioned before.) > What I want to know is, are the displayed values for CA and CT > correct, and can they be adjusted independently of each other? I believe this is a bug which I reported. If I remember properly, the problem is that the values are not being displayed correctly. -- 73, Vic, K2VCO Fresno CA http://www.qsl.net/k2vco _______________________________________________ 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 |
|
|
Vic and Drew,
The ATU in the K3 is a low-pass "L" design which has a series inductance and *either* an input (Ct) *or* output (Ca) shunting capacitance. There is only one capacitance in this desigh, not two. The single capacitance is switched between the input (Ct side - transceiver) or output (Ca side - antenna) of the inductance. So, when you are in CONFIG:KAT3 --> LCSET --> ATU TUNE, tapping ANT switches the capacitance between the input and output of the inductance. You can hear the relay switch when tapping ANT and sometimes hear a distinct difference in the received signal. In general the capacitance will need to be on the input (Ct) side when the antenna impedance is below 50 ohms and on the output side when the antenna impedance is greater than 50 ohm. You can look at the circuit design in the K3 schematics (documentation page on the web) if you would like to get a more detailed understanding. Or, you could also look at a program like TLW (transmission line wizard) that will calculate and show you a picture of the correct values for a low-pass "L" ATU with any given values of antenna impedances. Hope this helps! 73, Chuck, AE4CW
---
Chuck, AE4CW |
|
|
Ok, Chuck, thanks alot. That explains all. I was thinking it was a pi
with two capacitors. So anyway, for BCB reception, the capacitor doesn't do much and you would pretty much want to have maximum L, right? 73, Drew AF2Z On Sat, 19 Jul 2008 09:03:02 -0700 (PDT), Chuck, AE4CW wrote: > >Vic and Drew, > >The ATU in the K3 is a low-pass "L" design which has a series inductance and >*either* an input (Ct) *or* output (Ca) shunting capacitance. There is only >one capacitance in this desigh, not two. The single capacitance is switched >between the input (Ct side - transceiver) or output (Ca side - antenna) of >the inductance. So, when you are in CONFIG:KAT3 --> LCSET --> ATU TUNE, >tapping ANT switches the capacitance between the input and output of the >inductance. You can hear the relay switch when tapping ANT and sometimes >hear a distinct difference in the received signal. > >In general the capacitance will need to be on the input (Ct) side when the >antenna impedance is below 50 ohms and on the output side when the antenna >impedance is greater than 50 ohm. > >You can look at the circuit design in the K3 schematics (documentation page >on the web) if you would like to get a more detailed understanding. Or, >you could also look at a program like TLW (transmission line wizard) that >will calculate and show you a picture of the correct values for a low-pass >"L" ATU with any given values of antenna impedances. > >Hope this helps! 73, > >Chuck, AE4CW > _______________________________________________ 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 |
|
|
Drew,
For BCB operation using a 100 ft wire for an antenna (hopefully you also connect to some form of ground screen), I would expect the inductance in the KAT3 to be quite low. I would suggest adding a supplemental inductor in series with the antenna wire. I am not going to suggest just how much, but you can experiment. Using an antenna analyzer might be informative if you can find one that goes that low. 73, Don W3FPR [hidden email] wrote: > Ok, Chuck, thanks alot. That explains all. I was thinking it was a pi > with two capacitors. > > So anyway, for BCB reception, the capacitor doesn't do much and you > would pretty much want to have maximum L, right? > > 73, > Drew > AF2Z > > > On Sat, 19 Jul 2008 09:03:02 -0700 (PDT), Chuck, AE4CW wrote: > > >> Vic and Drew, >> >> The ATU in the K3 is a low-pass "L" design which has a series inductance and >> *either* an input (Ct) *or* output (Ca) shunting capacitance. There is only >> one capacitance in this desigh, not two. The single capacitance is switched >> between the input (Ct side - transceiver) or output (Ca side - antenna) of >> the inductance. So, when you are in CONFIG:KAT3 --> LCSET --> ATU TUNE, >> tapping ANT switches the capacitance between the input and output of the >> inductance. You can hear the relay switch when tapping ANT and sometimes >> hear a distinct difference in the received signal. >> >> In general the capacitance will need to be on the input (Ct) side when the >> antenna impedance is below 50 ohms and on the output side when the antenna >> impedance is greater than 50 ohm. >> >> You can look at the circuit design in the K3 schematics (documentation page >> on the web) if you would like to get a more detailed understanding. Or, >> you could also look at a program like TLW (transmission line wizard) that >> will calculate and show you a picture of the correct values for a low-pass >> "L" ATU with any given values of antenna impedances. >> >> Hope this helps! 73, >> >> Chuck, AE4CW >> >> > > _______________________________________________ > 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 > > No virus found in this incoming message. > Checked by AVG - http://www.avg.com > Version: 8.0.138 / Virus Database: 270.5.2/1561 - Release Date: 7/18/2008 6:35 PM > > > > 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 |
|
|
I forced my MFJ analyser to work in the broadcast band by simply adding a
silver mica cap in parallel with the tuning cap. David G3UNA > Drew, > > For BCB operation using a 100 ft wire for an antenna (hopefully you also > connect to some form of ground screen), I would expect the inductance in > the KAT3 to be quite low. I would suggest adding a supplemental inductor > in series with the antenna wire. I am not going to suggest just how much, > but you can experiment. Using an antenna analyzer might be informative if > you can find one that goes that low. > > 73, > Don W3FPR > 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 [K3]
|
1 view|%1 views
| Free forum by Nabble | Edit this page |