This is a multi-part message in MIME format.
------=_NextPart_000_0098_01BE0381.29172600
Content-Type: text/plain;
charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable
ZS5JF Wrote:
=20
=20
Hi all - let's start a new discussion topic. I am generally considered =
a reliable source of info but I have to admit that my experience on hf =
is limited. Well to the question and I would like all to consider this =
one.
I will only have the time and money to build one hf amplifier and would =
like constructive inputs for the initial thoughts I have.
Power supply I can happily tackle but the rf deck is the trickiest.
I have the following parts already.=20
Tube - Mullard / Philips QY5-3000A (tetrode - don't get confused by the =
5 in the part number) plate dissipation 3000W. Fmax =3D 220 MHz and =
rated for SSB operation. (Was used for tv ultra-linear duty on band 3 =
170 - 220 MHz in the UK). Vmax =3D 5kV and g2max =3D 1kV. Mullard data =
gives an output of 1,5kW at 30 MHz ssb duty with IMD typically 33 to 42 =
dB. Plus, I have the base and g2 decoupling gear from an old tv =
broadcast transmitter. Other tube specs I can post if needed.
Tank inductor - big (about 4" dia and 12" long) probably suitable for =
the low bands. Others I can wind from 1/4" copper tube which I have on =
hand.
Various variable capacitors - none really suitable for the anode tuning =
but probably OK for load capacitor duty. Best one about 250pF with =
approx. 6kV rating - tested at 8kV dc.
Several high power vacuum relays - about 10kV is the highest rating.
Lots of high voltage / current rf fixed capacitors.
Suitable blower - blows the QSL cards off the wall at 10 feet and =
frightens the dog!
Now - why can't I build the tank circuit using the vacuum relays to =
switch in fixed capacitors for each band. I have enough relays for this =
if one uses 160m, 80m, 40m, 20m, 15m and 10m. (My transceiver doesn't =
have the new WARC bands so I don't need to include them initially). =
Using a relatively small vacuum variable for the anode tuning and =
eliminating the normal tank circuit band-switch seems to me to be the =
way to go, in view of the problems some amplifiers suffer from.
Overall physical size doesn't really matter. (The power supply will be =
a separate item for versatility). I can have the required metal-work =
fabricated locally by a craftsman I know. (Rather have enough room to =
make the thing work efficiently than try and jam it all into a box which =
happens to be available). I plan to pressurise the anode compartment =
and use a scheme similar to the K2RIW design for 432 MHz with a chimney =
for the exhaust.
Basic spec. At least 1kW out on ssb or cw - with no strain. =20
Yes - We should shortly get a 1kW licence class here. (I have just =
finished writing the new regulations for the R.A. and part of the regs =
covers IMD and not running an amplifier at it's limit and removing the =
silly existing regulation which makes it an offence to own an amplifier =
capable of more than 400W! - so big amplifiers will become the order of =
the day).
Finally - If possible, the amplifier should also operate on 6m with =
similar output.
Anyway, is there a flaw I haven't spotted. Come on guys what have I =
missed. All ideas considered.
John ZS5JF
-------------------------------------------------------------------------=
-------------------------------------------------------------------------=
Hi John and all others,
=20
Have been "tagged off" the reflector for a while, but now back in =
business.
First, congrats to your exellent tube! It=B4s a real workhorse!!
=20
Myself I=B4m right now on my third project using Philips equavilent for =
that tube; QBL 5/3500.
This time I=B4ve found a QBL 5/4000 wich has a bigger platecooler and =
its platedissipation is
4 KW instead of 3,5KW.
=20
Guess your datasheet gives you quite moderate figures.... you easily can =
drive that tube to
1.5 A in SSB/CW service. with a efficient of lets say 55% its quite easy =
to calculate estimated
output....
=20
Myself, I have built all three amps using G2DAF design. A very clever =
and clean design wich
I highly recommend! If you are interested I can mail you some drawings =
as well as plots from
IMD measurements....=20
You wont have any problems to get full output at 50 MHz, with proper =
design, as the tube is rated
full output to 175MHz.
=20
73s de Lars SM3BDZ
=20
=20
------=_NextPart_000_0098_01BE0381.29172600
Content-Type: text/html;
charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable
<!DOCTYPE HTML PUBLIC "-//W3C//DTD W3 HTML//EN">
<HTML>
<HEAD>
<META content=3Dtext/html;charset=3Diso-8859-1 =
http-equiv=3DContent-Type>
<META content=3D'"MSHTML 4.72.3110.7"' name=3DGENERATOR>
</HEAD>
<BODY bgColor=3D#ffffff>
<DIV>
<DIV><FONT size=3D2>ZS5JF Wrote:</FONT></DIV>
<DIV><FONT color=3D#000000 face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT color=3D#000000 face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT color=3D#000000 face=3DArial size=3D2>Hi all - let's start a =
new discussion=20
topic. I am generally considered a reliable source of info but I =
have to=20
admit that my experience on hf is limited. Well to the question =
and I=20
would like all to consider this one.<BR><BR>I will only have the time =
and money=20
to build one hf amplifier and would like constructive inputs for the =
initial=20
thoughts I have.<BR><BR>Power supply I can happily tackle but the rf =
deck is the=20
trickiest.<BR><BR>I have the following parts already. <BR><BR>Tube - =
Mullard /=20
Philips QY5-3000A (tetrode - don't get confused by the 5 in the part =
number)=20
plate dissipation 3000W. Fmax =3D 220 MHz and rated for SSB =
operation. =20
(Was used for tv ultra-linear duty on band 3 170 - 220 MHz =
in the=20
UK). Vmax =3D 5kV and g2max =3D 1kV. Mullard data gives an =
output of=20
1,5kW at 30 MHz ssb duty with IMD typically 33 to 42 dB. Plus, I =
have the=20
base and g2 decoupling gear from an old tv broadcast transmitter. =
Other=20
tube specs I can post if needed.<BR><BR>Tank inductor - big (about =
4" dia=20
and 12" long) probably suitable for the low bands. =
Others I can=20
wind from 1/4" copper tube which I have on hand.<BR><BR>Various =
variable=20
capacitors - none really suitable for the anode tuning but probably OK =
for load=20
capacitor duty. Best one about 250pF with approx. 6kV rating - =
tested at=20
8kV dc.<BR><BR>Several high power vacuum relays - about 10kV is the =
highest=20
rating.<BR><BR>Lots of high voltage / current rf fixed=20
capacitors.<BR><BR>Suitable blower - blows the QSL cards off the wall at =
10 feet=20
and frightens the dog!<BR><BR>Now - why can't I build the =
tank=20
circuit using the vacuum relays to switch in fixed capacitors for each=20
band. I have enough relays for this if one uses 160m, 80m, 40m, =
20m, 15m=20
and 10m. (My transceiver doesn't have the new WARC bands so I =
don't need=20
to include them initially). Using a relatively small vacuum =
variable for=20
the anode tuning and eliminating the normal tank circuit band-switch =
seems to me=20
to be the way to go, in view of the problems some amplifiers suffer=20
from.<BR><BR>Overall physical size doesn't really matter. (The =
power=20
supply will be a separate item for versatility). I can have the =
required=20
metal-work fabricated locally by a craftsman I know. (Rather have =
enough=20
room to make the thing work efficiently than try and jam it all into a =
box which=20
happens to be available). I plan to pressurise the anode =
compartment and=20
use a scheme similar to the K2RIW design for 432 MHz with a chimney for =
the=20
exhaust.<BR><BR>Basic spec. At least 1kW out on ssb or cw - with =
no=20
strain. <BR><BR>Yes - We should shortly get a 1kW licence class=20
here. (I have just finished writing the new regulations for the =
R.A. and=20
part of the regs covers IMD and not running an amplifier at it's limit =
and=20
removing the silly existing regulation which makes it an offence to own =
an=20
amplifier capable of more than 400W! - so big amplifiers will =
become the=20
order of the day).<BR><BR>Finally - If possible, the amplifier should =
also=20
operate on 6m with similar output.<BR><BR>Anyway, is there a flaw =
I=20
haven't spotted. Come on guys what have I missed. All ideas=20
considered.<BR><BR>John=20
ZS5JF<BR>----------------------------------------------------------------=
-------------------------------------------------------------------------=
---------<BR><BR>Hi=20
John and all others,</FONT></DIV>
<DIV><FONT color=3D#000000 face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT color=3D#000000 face=3DArial size=3D2>Have been "tagged =
off" the=20
reflector for a while, but now back in business.</FONT></DIV>
<DIV><FONT color=3D#000000 face=3DArial size=3D2></FONT><FONT =
color=3D#000000=20
size=3D2>First, congrats to your exellent tube! It´s a real=20
workhorse!!</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>Myself I´m right now on my third project using =
Philips=20
equavilent for that tube; QBL 5/3500.</FONT></DIV>
<DIV><FONT size=3D2>This time I´ve found a QBL 5/4000 wich has a =
bigger=20
platecooler and its platedissipation is</FONT></DIV>
<DIV><FONT size=3D2>4 KW instead of 3,5KW.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT color=3D#000000 size=3D2>Guess your datasheet gives you quite =
moderate=20
figures.... you easily can drive that tube to</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2></FONT><FONT size=3D2>1.5 A in =
SSB/CW service.=20
with a efficient of lets say 55% its quite easy to calculate=20
estimated</FONT></DIV>
<DIV><FONT size=3D2>output....</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>Myself, I have built all three amps using G2DAF =
design. A very=20
clever and clean design wich</FONT></DIV>
<DIV><FONT size=3D2>I highly recommend! If you are interested I can mail =
you some=20
drawings as well as plots from</FONT></DIV>
<DIV><FONT size=3D2>IMD measurements.... </FONT></DIV>
<DIV> </DIV>
<DIV><FONT color=3D#000000 face=3DArial size=3D2>You wont have any =
problems to get=20
full output at 50 MHz, with proper design, as the tube is =
rated</FONT></DIV>
<DIV><FONT color=3D#000000 face=3DArial size=3D2>full output to =
175MHz.</FONT></DIV>
<DIV><FONT color=3D#000000 face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>73s de Lars SM3BDZ</FONT></DIV>
<DIV><FONT color=3D#000000 face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT color=3D#000000 face=3DArial=20
size=3D2><BR></FONT> </DIV></DIV></BODY></HTML>
------=_NextPart_000_0098_01BE0381.29172600--
--
FAQ on WWW: http://www.contesting.com/ampfaq.html
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|