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: Prev 1 2 3 [4]   Go Down
  Print  
Author Topic: Amplifier suggestions  (Read 2840 times)
K6BRN
Member

Posts: 1261




Ignore
« Reply #45 on: May 14, 2019, 05:54:35 AM »

Quote
I see Brian has created a smoke screen rebuttal to try and cover his tracks  Grin

(Cough!  Cough!)  Yes.  Quite a smoke screen.  45 casual contacts from New Zealand to Aruba and across the US on 30M and 80M last night, while having a late dinner, running 350 watts on 30M and 250 watts on 80M from my Yaesu Quadra AMPLIFIER, which follows my FTDX-3000 around like a puppy from band to band and never misses a beat.  On the EFHW.  Only about 10 contacts on the TA-33-MW Yagi on 20M and 40M.  Just how it worked out last night.

Quote
Those of us that have designed antenna systems with lobes pointing where we want to work and to handle the power we can use KNOW the difference it makes.  The moral of the story is EXPERIMENT.  FIND OUT what works for YOUR QTH.

Yes.  Exactly.  And more than one antenna, which can provide coverage across all bands means more ability to leverage good propagation and good operating conditions band by band (i.e. not TOO crowded, just crowded enough) maximizing contacts.

With a wire, how the antenna is installed - especially its height and shape, makes a major difference.  23 ft  in a horizontal V seems to work very well for me.   And amplifiers?  Yep.  really helps in a down cycle.  Legal limit mandatory?  Not so far.

Brian - K6BRN
Logged
N0YXB
Member

Posts: 1542




Ignore
« Reply #46 on: May 14, 2019, 09:27:48 AM »

Over the last 56 years that I have had a licence, I've used a large number of end fed antennas. Strangely, the most successful was a W3EDP!

Interesting, thanks!
Logged
G3RZP
Member

Posts: 1214




Ignore
« Reply #47 on: May 14, 2019, 10:52:39 AM »

W9IQ said:

Quote
ICAS of amplifiers has nothing to do with my comment other than it is the same false claim circle of most end fed antenna ratings.

As far as ICAS and CCS  ratings are concerned, see RCA Ham Tips for October 1939 at
http://n4trb.com/AmateurRadio/RCA_Ham_Tips/issues/rcahamtips0205.pdf

That explains why and how ICAS ratings are applicable to transmitting tubes: to my mind, applying it to antennas and RF transformers and antenna tuners  etc without defining exactly the parameters involved is meaningless BS. The manufacturer should define maximum power on what mode and maximum transmit time without damage or performance degradation: to do anything else is meaningless.
Logged
W9IQ
Member

Posts: 3210




Ignore
« Reply #48 on: May 14, 2019, 03:58:54 PM »

Peter,

I couldn't agree more.

- Glenn W9IQ
Logged

- Glenn W9IQ

I never make a mistake. I thought I did once but I was wrong.
W9IQ
Member

Posts: 3210




Ignore
« Reply #49 on: May 14, 2019, 04:01:14 PM »

Brian,

You rambled on but didn't answer the question. Can your 2K transformer handle the legal limit?

- Glenn W9IQ
Logged

- Glenn W9IQ

I never make a mistake. I thought I did once but I was wrong.
K6BRN
Member

Posts: 1261




Ignore
« Reply #50 on: May 14, 2019, 05:08:41 PM »

Peter (G3RZP):

Quote
That explains why and how ICAS ratings are applicable to transmitting tubes: to my mind, applying it to antennas and RF transformers and antenna tuners  etc without defining exactly the parameters involved is meaningless BS.

We certainly agree on that!

Glenn (W9IQ):

Quote
Can your 2K transformer handle the legal limit?

My own direct experience is limited to a bit over 1KW SSB with modest speech compression.  I do not have a legal limit amp to push this further.  At these levels I have not experienced any SWR change issues from 10M through 80M on the EFHW-8010-2K.  On SSB, I often run at or near this power level.

Best answer I can give to your question that I have actual, direct knowledge of.

Now I feel free to ramble....(again)

Based on my use experience, EFHW power limitations become important on high duty cycle modes where AVERAGE power is high and duty cycle is LONG.  The matching trnsformers do not seem to fail due to arcing the way antenna traps often can, but rather due to heating - which is why I was interested in your examination of failed transformers.  Have you see otherwise?

Significant power averaging due to thermal mass seems to happen with no transformer damage as the TX period drops below 30 seconds, with symmetrical RX periods.  Above 30 seconds at the power levels/modes shown below, SWR can change (rise OR fall), leading to a type of thermal runaway and matching transformer damage if not monitored/controlled.  So, when operating t or near these limits, I keep my eye on the SWR meter of my LP-700 or WN-2d and this gives me LOTS of warning before runaway becomes pronounced.

 With an EFHW-8010-2K antenna up about 18-23 feet (height makes a significant difference - less transfomer heating) my observed power limits are:

JT65/FT8/RTTY (short QSO):

80M: 275W
40M: 325W
30M: 450W
20-10M: 500W (amplifier spec. limit in these modes)

SSB:

80-10M:  1KW

At QTH#2 where the antenna is up only 15 feet, power limits are about 10% lower.  Experiments I've run suggest matching transformer power tolerance drops rapidly below 12 feet, limiting power applied much more on lower frequency bands.

So, there is a direct correlation in my experience between EFHW-8010-2K power handling and frequency/height.

The lower the frequency and/or height, the less power the matching transformer can tolerate.

The higher the frequency and/or height, the more power the matching transformer can tolerate.

Best Regards,

Brian Clebowicz


Logged
N6TRU
Member

Posts: 5




Ignore
« Reply #51 on: May 15, 2019, 06:06:18 PM »

Maybe I'll just stick to preparing my ham shack for high power operation for now. As I've mentioned previously, I don't have enough room to support typical antennas, so that's a challenge. I essentially only have room for an end fed antenna and perhaps smaller wire antennas. And I have experimented with different antennas, it's just been quite difficult to find an antenna that fits properly, especially since the roof is essentially off limits and antennas need elevation. Have any of you had any experiences with the Balun Designs Model 4935 - 4 & 9:1 Unun? It can supposedly handle 5kW. Would that be sufficient?

Thanks, Truman N6TRU
Logged
Pages: Prev 1 2 3 [4]   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!