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Today's Topics:
1. Re: Henry 3 KD Premier with 8877 (MU 4CX250B)
2. Re: new amp race (donroden@hiwaay.net)
3. new amp race / antenna take-off angle (Jim Thomson)
4. Re: new amp race / antenna take-off angle (Alek Petkovic)
5. Re: new amp race / antenna take-off angle (Martin Sole)
6. new amp race (Jim Thomson)
----------------------------------------------------------------------
Message: 1
Date: Mon, 22 May 2017 15:53:24 -0600
From: MU 4CX250B <4cx250b@miamioh.edu>
To: TexasRF@aol.com
Cc: "jmiklos@windstream.net" <jmiklos@windstream.net>,
"amps@contesting.com" <amps@contesting.com>
Subject: Re: [Amps] Henry 3 KD Premier with 8877
Message-ID: <1705483551472352915@unknownmsgid>
Content-Type: text/plain; charset="UTF-8"
I'm not familiar with that particular amplifier, but low 10m
efficiency is a common problem with 8877 amplifiers. In one of my
homebrew amplifiers, I had low efficiency in the 40% range until,
following a suggestion from Bob Sutherland W6PO, I relocated the tuned
pi input circuit capacitor C2 from the input band switch directly to
the cathode pin on the tube. Incredibly, efficiency jumped up into the
60% range. I was dumbfounded.
73,
Jim w8zr
Sent from my iPhone
On May 22, 2017, at 3:45 PM, Gerald Williamson via Amps <amps@contesting.com>
wrote:
Going back to the fundamentals: overall efficiency for class AB2 is
approximately .65 times (Qu - Ql) divided by Qu. Qu is unloaded Q and Ql is
loaded Q.
at 10m the Qu is higher because inductor losses are higher. In addition,
part of the inductance includes band switch leads and other leads between
tank circuit components. These leads are typically smaller causing losses to
increase. In addition, tune C has a minimum value that adds to the total C
and that increases the loaded Q which further increases losses.
Gerald K5GW
In a message dated 5/22/2017 4:14:25 P.M. Central Daylight Time,
jmiklos@windstream.net writes:
Does anyone have any first hand experience with this amplifier? I?m
particularly interested in the 10 meter performance (Eb, Ib, Pi, Po). Maximum
power output at .9A of Ib is only 1200 watts with efficiency at 43%. The
lower frequencies are more typical for an 8877, ie, 1500 watts out with
efficiency around 64% and Ib at .75A. Any theories to explain the low
efficiency on 10?
73?s
Buzz
Buzz Miklos WA4GPM
2043 Hawkcrest Drive E
Saint Johns, FL 32259
570-974-7433
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------------------------------
Message: 2
Date: Mon, 22 May 2017 18:50:08 -0500
From: donroden@hiwaay.net
To: amps@contesting.com
Subject: Re: [Amps] new amp race
Message-ID:
<20170522185008.Horde.qgk9Lkyai5-DvV8HCgfEqEE@webmail.hiwaay.net>
Content-Type: text/plain; charset=utf-8; format=flowed; DelSp=Yes
Quoting donroden <donroden@hiwaay.net>:
Bought a WSPRLite transmitter... amazing to see vk and zl reporting
way above noise using 50 mw....Yes 1/5 of a watt.
For you math majors that let this slip by, 50mw is 1/20th of a watt...
On the way to work today, I realized my mistake.
Don W4DNR
DonR
------------------------------
Message: 3
Date: Tue, 23 May 2017 05:01:06 -0700
From: "Jim Thomson" <jim.thom@telus.net>
To: <amps@contesting.com>
Subject: [Amps] new amp race / antenna take-off angle
Message-ID: <442DCCB15873408CA16E83805473823E@JimPC>
Content-Type: text/plain; charset="iso-8859-1"
Date: Sun, 21 May 2017 19:14:09 +0930
From: "Leigh Turner" <invertech@frontierisp.net.au>
To: "'AMPS'" <amps@contesting.com>
Subject: Re: [Amps] new amp race / antenna take-off angle
<Precisely correct Peter!
If the HF antenna lobe take-off angle is fortuitously optimal for enabling a
given DX hop path then QRP Tx power will wing it!
No amount of Tx power or Rx sensitivity / SNR will compensate if this sweet
spot in the prevailing ephemeral propagation path is missed...
73
Leigh
VK5KLT
## Both VK land + germany have a 10 meter... aka 33 foot height limit. That
now effectively
just destroyed amateur radio. I dont know what take off angle you are
blathering on about leigh.
At just 33 ft with your height restriction.... the only angle you are gonna
have is either straight up...
or into the side of you neigbours home. 33 ft will not clear anything, and
is 100% ineffective.
Utility poles around na are typ 40 ft high, with the hv wire another 1.5 ft
above that. The typ home,
with its well grounded chicken mesh, just beneath the stucco. Toss in your
400 watt useless ..legal
limit, and you are doomed to failure.
Jim VE7RF
------------------------------
Message: 4
Date: Tue, 23 May 2017 20:20:50 +0800
From: Alek Petkovic <vk6apk@bigpond.com>
To: AMPS <amps@contesting.com>
Subject: Re: [Amps] new amp race / antenna take-off angle
Message-ID: <59242922.4020206@bigpond.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Not in this part of there world, there ain't no 10m limit.
Most suburban masts are around 15m to 20m high. All applications are
assessed on an individual basis. There are moves afoot to have a 10m
minimum ratified across the country but that has not happened yet. If it
does, it means, you will not have to ask for permission to put up a mast
of that height. Anything bigger, you'll have to ask.
Of course, in rural areas, the sky is the limit.
73, Alek.
VK6APK
On 23/05/2017 8:01 PM, Jim Thomson wrote:
Date: Sun, 21 May 2017 19:14:09 +0930
From: "Leigh Turner"<invertech@frontierisp.net.au>
To: "'AMPS'"<amps@contesting.com>
Subject: Re: [Amps] new amp race / antenna take-off angle
<Precisely correct Peter!
If the HF antenna lobe take-off angle is fortuitously optimal for enabling a
given DX hop path then QRP Tx power will wing it!
No amount of Tx power or Rx sensitivity / SNR will compensate if this sweet
spot in the prevailing ephemeral propagation path is missed...
73
Leigh
VK5KLT
## Both VK land + germany have a 10 meter... aka 33 foot height limit. That
now effectively
just destroyed amateur radio. I dont know what take off angle you are
blathering on about leigh.
At just 33 ft with your height restriction.... the only angle you are gonna
have is either straight up...
or into the side of you neigbours home. 33 ft will not clear anything, and
is 100% ineffective.
Utility poles around na are typ 40 ft high, with the hv wire another 1.5 ft
above that. The typ home,
with its well grounded chicken mesh, just beneath the stucco. Toss in your
400 watt useless ..legal
limit, and you are doomed to failure.
Jim VE7RF
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