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Hi all,
Tomorrow I'm going to see a friend?that has some kind of problem with his LK-450 NT amp. At this time I have no idea what the problem is due to inconsistent?information.
But I have a question, I've never worked on one of these but I'm assuming the network is very broad banded and you only adjust a "fine tune" for your operating frequency.
My common sense tells me that inside there must be some kind of "broader" (lack of a better term) adjustment inside to get the network in the ballpark so a fine tune can dial it in. I'm thinking that especially on 160 and 80/75 it would be critical to get it close for either the top of the bands or the bottom of the bands.
Am I on the right track? Also, is there any known common problems I should?be aware of?
Thanks all. Bob? W4JFA
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All the LK series NT ( no tune) amps have several small load and tune capacitors. You must pre select the frequencies you want to operate on each band first. ?Then you use the internal load and tune caps to load the amp up for those frequencies per band. ?Once you pre load the amp on the various bands you will only get a marginal excursion from the?selected frequency to an off frequency away from that. ?You will never get?coverage of the bottom and top of the band. ?As far as I’m concerned these amps are only good for ops that ONLY frequent certain frequencies on each band, like net control operators. ?Anyone wanting the freedom of the whole band with full power output would never want these amps. The loading process is pretty tedious because it has so be done with a long flat blade screwdriver and I think it needs to be done in a certain order but that’s I’m not sure of.
On Monday, March 25, 2024, 12:58 PM, Bob <W4JFABob@...> wrote: Hi all,
Tomorrow I'm going to see a friend?that has some kind of problem with his LK-450 NT amp. At this time I have no idea what the problem is due to inconsistent?information.
But I have a question, I've never worked on one of these but I'm assuming the network is very broad banded and you only adjust a "fine tune" for your operating frequency.
My common sense tells me that inside there must be some kind of "broader" (lack of a better term) adjustment inside to get the network in the ballpark so a fine tune can dial it in. I'm thinking that especially on 160 and 80/75 it would be critical to get it close for either the top of the bands or the bottom of the bands.
Am I on the right track? Also, is there any known common problems I should?be aware of?
Thanks all. Bob? W4JFA
|
That is very odd. ..? I have owned several LK amps.? They will cover the entire band in the No tune.? The SWR needs to be fairly low however, Most people do not have an antenna that covers the entire band anyways.
Some models have a switch for 160 and 80 to cover the entire band.? Its two presets per on those bands.??
Also, my Alpha 374A works the same way. It also covers the entire band.
I think the reason why some people don't like them is?because they feel they are missing something by not tuning up to max power each time.
Who the hell wants to retune a damn amp 20 times an hour moving around from band to band and from low to high on the bands.? Nobody.? It ruins the fun of working DX.
These things are really nice and have a huge convenience factor. At the expense of some peak power output.?
Another huge advantage is some OPS, NO MATTER WHAT, will never tune the amp correctly.? They will mistune it, Burn it down, over and over and over. NT amps remove all of that.? The OM can just key down and operate with little risk of blowing the amp up.
For 1kw or so this kind of amp is really nice and fun to use.
C
toggle quoted message
Show quoted text
All the LK series NT ( no tune) amps have several small load and tune capacitors. You must pre select the frequencies you want to operate on each band first. ?Then you use the internal load and tune caps to load the amp up for those frequencies per band.
?Once you pre load the amp on the various bands you will only get a marginal excursion from the?selected frequency to an off frequency away from that. ?You will never get?coverage of the bottom and top of the band. ?As far as I’m concerned these amps are only
good for ops that ONLY frequent certain frequencies on each band, like net control operators. ?Anyone wanting the freedom of the whole band with full power output would never want these amps.
The loading process is pretty tedious because it has so be done with a long flat blade screwdriver and I think it needs to be done in a certain order but that’s I’m not sure of.
On Monday, March 25, 2024, 12:58 PM, Bob <W4JFABob@...> wrote:
Hi all,
Tomorrow I'm going to see a friend?that has some kind of problem with his LK-450 NT amp.
At this time I have no idea what the problem is due to inconsistent?information.
But I have a question, I've never worked on one of these but I'm assuming the network is
very broad banded and you only adjust a "fine tune" for your operating frequency.
My common sense tells me that inside there must be some kind of "broader" (lack of a better term) adjustment inside to get the network in the ballpark so a fine tune can dial it in.
I'm thinking that especially on 160 and 80/75 it would be critical to get it close for either the top of the bands or the bottom of the bands.
Am I on the right track? Also, is there any known common problems I should?be aware of?
Thanks all. Bob? W4JFA
|
I'll let you guys know what I find. I'll see it Tues eve. Bob W4JFA?
On Mon, Mar 25, 2024, 4:25 PM W7WRX < clark@...> wrote:
That is very odd. ..? I have owned several LK amps.? They will cover the entire band in the No tune.? The SWR needs to be fairly low however, Most people do not have an antenna that covers the entire band anyways.
Some models have a switch for 160 and 80 to cover the entire band.? Its two presets per on those bands.??
Also, my Alpha 374A works the same way. It also covers the entire band.
I think the reason why some people don't like them is?because they feel they are missing something by not tuning up to max power each time.
Who the hell wants to retune a damn amp 20 times an hour moving around from band to band and from low to high on the bands.? Nobody.? It ruins the fun of working DX.
These things are really nice and have a huge convenience factor. At the expense of some peak power output.?
Another huge advantage is some OPS, NO MATTER WHAT, will never tune the amp correctly.? They will mistune it, Burn it down, over and over and over. NT amps remove all of that.? The OM can just key down and operate with little risk of blowing the amp up.
For 1kw or so this kind of amp is really nice and fun to use.
C
All the LK series NT ( no tune) amps have several small load and tune capacitors. You must pre select the frequencies you want to operate on each band first.? Then you use the internal load and tune caps to load the amp up for those frequencies per band.
?Once you pre load the amp on the various bands you will only get a marginal excursion from the?selected frequency to an off frequency away from that.? You will never get?coverage of the bottom and top of the band.? As far as I’m concerned these amps are only
good for ops that ONLY frequent certain frequencies on each band, like net control operators.? Anyone wanting the freedom of the whole band with full power output would never want these amps.
The loading process is pretty tedious because it has so be done with a long flat blade screwdriver and I think it needs to be done in a certain order but that’s I’m not sure of.
On Monday, March 25, 2024, 12:58 PM, Bob <W4JFABob@...> wrote:
Hi all,
Tomorrow I'm going to see a friend?that has some kind of problem with his LK-450 NT amp.
At this time I have no idea what the problem is due to inconsistent?information.
But I have a question, I've never worked on one of these but I'm assuming the network is
very broad banded and you only adjust a "fine tune" for your operating frequency.
My common sense tells me that inside there must be some kind of "broader" (lack of a better term) adjustment inside to get the network in the ballpark so a fine tune can dial it in.
I'm thinking that especially on 160 and 80/75 it would be critical to get it close for either the top of the bands or the bottom of the bands.
Am I on the right track? Also, is there any known common problems I should?be aware of?
Thanks all. Bob? W4JFA
|
Checked it out. Radio - amp - swr/per meter - dummy load. All fine. He had a cluster _____ of coax, switches to switch different antennas to ??? I showed him the radio and amp are fine so he has to work on all the antennas and switching etc. Bob W4JFA?
I'll let you guys know what I find. I'll see it Tues eve. Bob W4JFA?
On Mon, Mar 25, 2024, 4:25 PM W7WRX < clark@...> wrote:
That is very odd. ..? I have owned several LK amps.? They will cover the entire band in the No tune.? The SWR needs to be fairly low however, Most people do not have an antenna that covers the entire band anyways.
Some models have a switch for 160 and 80 to cover the entire band.? Its two presets per on those bands.??
Also, my Alpha 374A works the same way. It also covers the entire band.
I think the reason why some people don't like them is?because they feel they are missing something by not tuning up to max power each time.
Who the hell wants to retune a damn amp 20 times an hour moving around from band to band and from low to high on the bands.? Nobody.? It ruins the fun of working DX.
These things are really nice and have a huge convenience factor. At the expense of some peak power output.?
Another huge advantage is some OPS, NO MATTER WHAT, will never tune the amp correctly.? They will mistune it, Burn it down, over and over and over. NT amps remove all of that.? The OM can just key down and operate with little risk of blowing the amp up.
For 1kw or so this kind of amp is really nice and fun to use.
C
All the LK series NT ( no tune) amps have several small load and tune capacitors. You must pre select the frequencies you want to operate on each band first.? Then you use the internal load and tune caps to load the amp up for those frequencies per band.
?Once you pre load the amp on the various bands you will only get a marginal excursion from the?selected frequency to an off frequency away from that.? You will never get?coverage of the bottom and top of the band.? As far as I’m concerned these amps are only
good for ops that ONLY frequent certain frequencies on each band, like net control operators.? Anyone wanting the freedom of the whole band with full power output would never want these amps.
The loading process is pretty tedious because it has so be done with a long flat blade screwdriver and I think it needs to be done in a certain order but that’s I’m not sure of.
On Monday, March 25, 2024, 12:58 PM, Bob <W4JFABob@...> wrote:
Hi all,
Tomorrow I'm going to see a friend?that has some kind of problem with his LK-450 NT amp.
At this time I have no idea what the problem is due to inconsistent?information.
But I have a question, I've never worked on one of these but I'm assuming the network is
very broad banded and you only adjust a "fine tune" for your operating frequency.
My common sense tells me that inside there must be some kind of "broader" (lack of a better term) adjustment inside to get the network in the ballpark so a fine tune can dial it in.
I'm thinking that especially on 160 and 80/75 it would be critical to get it close for either the top of the bands or the bottom of the bands.
Am I on the right track? Also, is there any known common problems I should?be aware of?
Thanks all. Bob? W4JFA
|
Interestingly enough, after looking at the schematics for the 450/500/550 NT series of amplifiers,? they all use a PI network? on 160-10m.? ?BUT they use a lower, loaded Q.? ( more coil, less tune + load C).?
The alpha 78/ 374A etc, in broadband mode, ( and? also manual tune),? all use a PI-L..... same deal though, a lower loaded Q is used, when switching from 'manual tune'? to ....'broadband'.? ?In broadband mode, more L is used on 80-40-20-15m.?
The broadband feature on the alpha amps only works on 80-15m.? Strictly manual tune on 160+10m.?
?
I asked glen, AE0Q, the alpha fellow, why they didn't use the same deal on their newer amps (9500 / 8410).? He said the 78/374A? etc, had lower eff vs manual tuning.? So they switched to motor driven tune + load caps..and the bandswitch.?
?
Funny thing is, on one of my older 4-1000 amps, with the roller coil in it? ( and also my 3x3 with a roller).... when normal? Q used ( this is a PI), like 12-15, PO was good.? But then tried increasing the uh on the roller a bit ( and slightly less on the tune + load caps)..and PO increased.? ?So repeated the process again, with more uh, less tune and load C..and again, PO increased.? Repeated several more times, in small increments, ( each time retuning the amp with the same drive level)...and PO kept on increasing, Then no more PO with any further increases in uh.? ?It just flat lined with max PO, regardless of how much uh was dialed in.?
So I backed down the uh, until PO just started to drop off a few watts.... and left it there. This was all on 75m.? ?Same deal on the other bands.? ?The idea here is to use a lower Q...but just low enough to do the job.? ?Go too low, and PO stays the same, (no more increase) even more broad banded, but I highly suspect the harmonic suppression is severely de-graded.?
?
There is NO spec for harmonic suppression in the online manual for the 450/500/550? (which also covers the NT versions).? ?
?
It would be interesting to know what the actual harmonic suppression is on each band on the NT versions.?
|
On the 374A, 10 meters is just the Load cap. Its fixed tune.? So if you set the load cap to like 70 on the dial, You get instant 10, 15,20,40 and 80 with no tuning.??
I/we noticed the same thing on my 2x 3-1000Z amp.? Not sure if you remember.? I kept "walking" the coil and each time got more power. Eventually, increase stopped.? This makes a huge difference on higher bands.??
I also noticed this phenomenon can occur with the combo of Tune and load cap.? ?I like to "walk" the load cap in fixed degrees and peak the tune. There is a perfect spot. It will fall off on either side.
I am unsure why this happens.? It does happen on Most henry amps and the alphas. This does NOT occur on the SB220 for example. The load has one peak and its broad and soft.
The 2k4A was really bad about this. If you just dialed up the tune and load for peak or carrier. You would be sure to be way OFF.? Stepping the load control and adjusting tune again and you can find that sweet spot.
C
toggle quoted message
Show quoted text
Interestingly enough, after looking at the schematics for the 450/500/550 NT series of amplifiers,? they all use a PI network? on 160-10m.? ?BUT they use a lower, loaded Q.? ( more coil, less tune + load C).?
The alpha 78/ 374A etc, in broadband mode, ( and? also manual tune),? all use a PI-L..... same deal though, a lower loaded Q is used, when switching from 'manual tune'? to ....'broadband'.? ?In broadband mode, more L is used on 80-40-20-15m.?
The broadband feature on the alpha amps only works on 80-15m.? Strictly manual tune on 160+10m.?
?
I asked glen, AE0Q, the alpha fellow, why they didn't use the same deal on their newer amps (9500 / 8410).? He said the 78/374A? etc, had lower eff vs manual tuning.? So they switched to motor driven tune + load caps..and the bandswitch.?
?
Funny thing is, on one of my older 4-1000 amps, with the roller coil in it? ( and also my 3x3 with a roller).... when normal? Q used ( this is a PI), like 12-15, PO was good.? But then tried increasing the uh on the roller a bit ( and slightly less on the
tune + load caps)..and PO increased.? ?So repeated the process again, with more uh, less tune and load C..and again, PO increased.? Repeated several more times, in small increments, ( each time retuning the amp with the same drive level)...and PO kept on increasing,
Then no more PO with any further increases in uh.? ?It just flat lined with max PO, regardless of how much uh was dialed in.?
So I backed down the uh, until PO just started to drop off a few watts.... and left it there. This was all on 75m.? ?Same deal on the other bands.? ?The idea here is to use a lower Q...but just low enough to do the job.? ?Go too low, and PO stays the same,
(no more increase) even more broad banded, but I highly suspect the harmonic suppression is severely de-graded.?
?
There is NO spec for harmonic suppression in the online manual for the 450/500/550? (which also covers the NT versions).? ?
?
It would be interesting to know what the actual harmonic suppression is on each band on the NT versions.?
|
I'm not sure if my answer came through so... I hooked up the amp through a power meter then dummy load. Amp is fine.
Thanks for the info guys.
Bob W4JFA?
On Thu, Mar 28, 2024, 12:15 PM W7WRX < clark@...> wrote:
On the 374A, 10 meters is just the Load cap. Its fixed tune.? So if you set the load cap to like 70 on the dial, You get instant 10, 15,20,40 and 80 with no tuning.??
I/we noticed the same thing on my 2x 3-1000Z amp.? Not sure if you remember.? I kept "walking" the coil and each time got more power. Eventually, increase stopped.? This makes a huge difference on higher bands.??
I also noticed this phenomenon can occur with the combo of Tune and load cap.? ?I like to "walk" the load cap in fixed degrees and peak the tune. There is a perfect spot. It will fall off on either side.
I am unsure why this happens.? It does happen on Most henry amps and the alphas. This does NOT occur on the SB220 for example. The load has one peak and its broad and soft.
The 2k4A was really bad about this. If you just dialed up the tune and load for peak or carrier. You would be sure to be way OFF.? Stepping the load control and adjusting tune again and you can find that sweet spot.
C
Interestingly enough, after looking at the schematics for the 450/500/550 NT series of amplifiers,? they all use a PI network? on 160-10m.? ?BUT they use a lower, loaded Q.? ( more coil, less tune + load C).?
The alpha 78/ 374A etc, in broadband mode, ( and? also manual tune),? all use a PI-L..... same deal though, a lower loaded Q is used, when switching from 'manual tune'? to ....'broadband'.? ?In broadband mode, more L is used on 80-40-20-15m.?
The broadband feature on the alpha amps only works on 80-15m.? Strictly manual tune on 160+10m.?
?
I asked glen, AE0Q, the alpha fellow, why they didn't use the same deal on their newer amps (9500 / 8410).? He said the 78/374A? etc, had lower eff vs manual tuning.? So they switched to motor driven tune + load caps..and the bandswitch.?
?
Funny thing is, on one of my older 4-1000 amps, with the roller coil in it? ( and also my 3x3 with a roller).... when normal? Q used ( this is a PI), like 12-15, PO was good.? But then tried increasing the uh on the roller a bit ( and slightly less on the
tune + load caps)..and PO increased.? ?So repeated the process again, with more uh, less tune and load C..and again, PO increased.? Repeated several more times, in small increments, ( each time retuning the amp with the same drive level)...and PO kept on increasing,
Then no more PO with any further increases in uh.? ?It just flat lined with max PO, regardless of how much uh was dialed in.?
So I backed down the uh, until PO just started to drop off a few watts.... and left it there. This was all on 75m.? ?Same deal on the other bands.? ?The idea here is to use a lower Q...but just low enough to do the job.? ?Go too low, and PO stays the same,
(no more increase) even more broad banded, but I highly suspect the harmonic suppression is severely de-graded.?
?
There is NO spec for harmonic suppression in the online manual for the 450/500/550? (which also covers the NT versions).? ?
?
It would be interesting to know what the actual harmonic suppression is on each band on the NT versions.?
|
Bob