Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

donate to eham
   Home   Help Search  
Pages: [1] 2 3 Next   Go Down
  Print  
Author Topic: al-811h load control fully clockwise on 80m  (Read 12680 times)
WY7CHY
Member

Posts: 957




Ignore
« on: May 09, 2016, 10:27:44 AM »

So, I've been tinkering with a new (used) AL-811H I picked up from a friend. So far, it seems to be working fine. Getting close to full 600 watts out on CW with about 65-70 watts input. Of course, I knock it back down to about 500 watts (55-60 watts input).

My question concerns loading on the 80m band. On the 40m, 20m, 17m bands (The only other ones I've played with), I can get close to the 600 watts in CW and tweaking load and plate looks good. On the 80m band however, the load maxes out at 10 (Fully Clockwise) and I'm getting around 500 watts max on CW. The grid current is safe, but it's about 180-190. I'm sure, like the other bands, at full output, I could get the grid down to about 160-175 if I had some more LOAD CONTROL to work with. Everything seems fine; just wondering why I might need full clockwise (10) on load.

I've retuned a number of times thinking maybe I was doing something wrong. I'm not. It's loading like the other bands. Just can't give it any more load. Therefore, I'm limited on output power because of the grid current, which I don't want to exceed.

Any ideas what I should look at; or do you think I simply have to live with it. I always thought the band to have problems with is the 10m band; not the 80m. Any thoughts? Thanks. Mike.
Logged

Born Wild - Raised Proud: 73
Cheyenne, Wyoming
K6AER
Member

Posts: 5689




Ignore
« Reply #1 on: May 09, 2016, 10:56:48 AM »

A couple of things come to mind.

At full load is that by the panel numbers or is the cap fully meshed?

Is your test load 50 ohms?
Logged
KD1I
Member

Posts: 466




Ignore
« Reply #2 on: May 09, 2016, 01:25:18 PM »

OK, without looking at a schematic, let me offer you my best SWAG.     For 80 meters, the band switch cuts in a fixed capacitor and this is not happening because of dirty contacts on the band switch. So check your schematic to see if that part is correct and if so, open the amp (after waiting a while unplugged. ground the high voltage just to be certain) and see if this is true.   It is a cheap and easy solution....and if I'm wrong, Oh, well.    Undecided   73, Jim
Logged
W1QJ
Member

Posts: 2945




Ignore
« Reply #3 on: May 09, 2016, 02:05:08 PM »

Yeah, like Jim said above, there should be a fixed cap which gets switched in on 80 meters.  I don't recall the value it is, maybe 200pf.  You have to make sure it is there #1.  I think I saw an older version of that amp where that cap was missing or t was the wrong value than what the schematic called for.  So check that "padding" capacitor for being there and #2 if it is good.  It could be bad, or the contacts that switch it in is bad.  Another thing could be the antenna.  If you have a dummy load try loading into that and see if it works OK into a dummy load.
Logged
WB2WIK
Member

Posts: 21836




Ignore
« Reply #4 on: May 09, 2016, 02:31:36 PM »

Isn't "fully clockwise" actually maximum loading, which is minimum capacitance?

That's normally the case with most amps.
Logged
W1QJ
Member

Posts: 2945




Ignore
« Reply #5 on: May 09, 2016, 04:13:40 PM »

Isn't "fully clockwise" actually maximum loading, which is minimum capacitance?

That's normally the case with most amps.

All Ameritron amps are fully meshed at 0 on the load log scale.  That is fully CCW.  Fully CW should be minimum capacitance (unmeshed) so if the load cap is at 10 on the log scale then someone may have changed the calibration.  ALL Ameritron amps should be MAX capacitance at full CCW or 0 on the log scale. 
Logged
WY7CHY
Member

Posts: 957




Ignore
« Reply #6 on: May 09, 2016, 09:57:14 PM »

Definitely a couple great ideas. I wish I read these replies earlier today. I had a burned out meter bulb, and I just retrofitted the light with a couple blue LED bulbs. I had everything apart. Oh well. I'm sure I'll have it opened up again later. I'll definitely check the band switch and the capacitor. I'm thinking the bandswitch is "Probably" good, but you never know. I say probably, because it tunes up and I can transmit good. Low SWR between the transceiver and the amp. Getting 500 watts out CW instead of 600 watts. That's not a big deal, but the loading I start off at "3" like the instructions say, and the grid current does go down and RF output does go up as I adjust the Load. But I have to go from 3 all the way up to 10; full load; and I can't go any further. At least I'm able to get decent amount of power out while keeping the grid current down.

Next time I have the case open, I'll check the switch for good continuity (Physical connection). I'll also check for the capacitor. The other bands; (Well, at least 40, 20, and 17m; because that's all I've really tried), all have the plate and load settings pretty close to where the manual says to start them. 80m is the only one off. Thanks; I'll probably get to it in a couple days. I'll let you know. Mike.
Logged

Born Wild - Raised Proud: 73
Cheyenne, Wyoming
WB2WIK
Member

Posts: 21836




Ignore
« Reply #7 on: May 10, 2016, 09:49:59 AM »

That's not a big deal, but the loading I start off at "3" like the instructions say, and the grid current does go down and RF output does go up as I adjust the Load. But I have to go from 3 all the way up to 10; full load; and I can't go any further. At least I'm able to get decent amount of power out while keeping the grid current down.



If you have to advance the LOAD fully CW and the alignment is not out of whack between the capacitor and the front panel knob/indicator, then your "load padding" cap for 80m must be there.   If it weren't, you'd need to adjust the load fully CCW for max LOAD capacitance, which is actually "minimum loading."

Does this happen with a good resistive 50 Ohm dummy load, or only with your antenna?
Logged
WY7CHY
Member

Posts: 957




Ignore
« Reply #8 on: May 10, 2016, 08:22:55 PM »

Everything seems to be good; just the loading is an issue. I went through all the other band. It's capable of 12/10m but I didn't try that. The 15, 17, 20. and 40 meters all tune the way they are suppose to. Matter of fact, the Plate and Load settings, are pretty darn close to how the instructions say to place them for initial setting prior to tuning. The 40m is a "Little" high in SWR between the transceiver and the amp, but I'm sure I can tune that without a problem. Not too high, just higher than the other bands. But that's not an issue.

Something I noticed is: When doing the tuning on 80m starting with 20 watts, adjusting plate I can max the output power and dip the plate current. If I do the Load tuning right then, I notice it affects the power like it's suppose to. Tweak a little, power goes up, go too far, power comes down. Increase input power to 30 watts, sort of the same thing. But around 40 watts in, is where I have to keep adding load to prevent too much grid current. In the end, I have Plate tuning setting about where it's suppose to be. (According to the book). Load tuning setting maxed out at 10. With about 50-55 watts in, I max out about 480-500 watts out. (CW/FM). Plate Current is safe at about 600ma. Grid current is safe at about 170-180ma. If I give any more input power, the grid current will go past the taboo 200ma and I have no more Load control to bring it down.

On a side note; not sure if it COULD have any bearing on this. While looking through at the tank coils (Recommended by Ameritron to look at), I looked at the input tuning and noticed the "Green Wire" cut. Basically, the ability for 10m operation. I haven't really researched the 10m mod, but could this have an relationship? I doubt it, because it doesn't affect any other band. Just something I noticed and was wondering. Thanks. Mike.
Logged

Born Wild - Raised Proud: 73
Cheyenne, Wyoming
W9IQ
Member

Posts: 3232




Ignore
« Reply #9 on: May 11, 2016, 04:03:39 AM »

Mike,

You have mentioned the SWR between your transceiver and the amp a couple of times in your posts. This is not particularly meaningful. A more useful metric is the SWR between the amplifier and the antenna since the loading adjustment is essentially attempting to match the amplifier to the antenna system.

You should repeat your tests into a dummy load to eliminate any variables from the antenna system. Do you have a dummy load that can take this power for short duration testing?

- Glenn W9IQ
Logged

- Glenn W9IQ

I never make a mistake. I thought I did once but I was wrong.
N3QE
Member

Posts: 5576




Ignore
« Reply #10 on: May 11, 2016, 04:28:44 AM »

Something I noticed is: When doing the tuning on 80m starting with 20 watts, adjusting plate I can max the output power and dip the plate current. If I do the Load tuning right then, I notice it affects the power like it's suppose to. Tweak a little, power goes up, go too far, power comes down. Increase input power to 30 watts, sort of the same thing. But around 40 watts in, is where I have to keep adding load to prevent too much grid current. In the end, I have Plate tuning setting about where it's suppose to be. (According to the book). Load tuning setting maxed out at 10. With about 50-55 watts in, I max out about 480-500 watts out. (CW/FM). Plate Current is safe at about 600ma. Grid current is safe at about 170-180ma. If I give any more input power, the grid current will go past the taboo 200ma and I have no more Load control to bring it down.

Having to advance the load control to keep grid current down, as drive is changed from 20W to 40W to 55W, is perfectly normal.

If the antenna's impedance is particularly low, you will have to advance the load control more.

And especially on the low bands, you'll find the knob has to turn more as well. Especially for a small amp with basic control ranges, the tuning seems "compressed" or "critical" on the high bands where a small change in knob position makes a big change in tuning, and "drawn out" on the low bands.

I don't see anything wrong with your amp.

If you are getting 500W out in a continuous carrier mode there's nothing wrong. Well, except for the "marketing ratings" of the amplifier, but Ameritron is hardly the worst offender there. (Other manufacturers sold their 4x811A amps as being kilowatt CW and 1.5kW PEP amps - admittedly input ratings back then.)
« Last Edit: May 11, 2016, 04:51:06 AM by N3QE » Logged
WY7CHY
Member

Posts: 957




Ignore
« Reply #11 on: May 11, 2016, 06:40:16 AM »

I only mentioned in general that the SWR was pretty much fine. Just to eliminate that as an issue. On 80m, the SWR is fine. BOTH between the transceiver and the amp (INPUT TUNING), as well as to the antenna. That's not an issue.

N3QE. I understand what you're saying, but I think this is a "Little" different than "normal". Of course advancing the load to reduce grid current is normal. I've simply posted that unlike ALL the other bands, I have to advance the load on 80m FULLY Clockwise. Considering the initial setting is at around "3", to have to advance it all the way to "10", and it still isn't "maxed" setting yet, is a bit curious.

All other bands, "Except 10m, I haven't tried that", plate and load do what it's suppose to. Peak and dip. Go too far one direction or the other and the readings change. The difference on the 80m band, is the plate works fine. It allows you to PEAK the output power. Go to far forward or back and it negatively affects it. Works great. The Load control on the other hand end stops at the full clockwise position. It's not a big thing. I can get a decent amount of power out and keep the grid current under control. But I should be able to "Peak" the settings. Peak output power; go to far forward or back and output power goes down.

So no, I don't think this sounds normal. Not compared to the other bands or the settings recommended in the manual. Again; it's not a major problem. Just something that's not normal.

Ameritron had me looking at the tank coil to see if it had changed value from heat; (having 2 of the loops in the coil touching each other. The tank coil looked fine. I'm waiting for Ameritron tech support to provide more info. It could be one of the caps on the band switch. Who knows.
Logged

Born Wild - Raised Proud: 73
Cheyenne, Wyoming
WB2WIK
Member

Posts: 21836




Ignore
« Reply #12 on: May 11, 2016, 09:22:47 AM »

Do you have a good resistive dummy load?

"The SWR is fine" as a load doesn't mean much.   Not the same as a resistor.

As a point of reference and information, always use a resistive dummy load to help debug output tuning issues.

Do you have one?
Logged
N1RND
Member

Posts: 56




Ignore
« Reply #13 on: May 11, 2016, 10:36:15 AM »

My 3 month old 811h that I bought new does the same thing.  Hmmm?  I don't use 80 so never checked it out.
Logged
WY7CHY
Member

Posts: 957




Ignore
« Reply #14 on: May 11, 2016, 11:10:15 AM »

N1RND; that's interesting; and "Good" to know. Like I mentioned, it's not hurting anything; other than not being able to max "Tweak" for that band. Usually, any adjustments should allow for TOO HIGH or for TOO LOW, and you find the spot in the middle what is best. Having the Load full Clockwise doesn't allow for the most accurate tuning.

Thanks for providing similar results. Mike.
Logged

Born Wild - Raised Proud: 73
Cheyenne, Wyoming
Pages: [1] 2 3 Next   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!