[hpsdr] Re Munin low output on 6m

Tue Dec 3 22:28:41 PST 2013

Hi Georg, about the capacitors you used, are they smt or the traditional ones with two wires sticking out ?

Thanks, Giovanni, IZ0SQZ
-----Original Message-----
From: Georg Prinz <getpri at t-online.de>
Sender: hpsdr-bounces at lists.openhpsdr.orgDate: Mon, 02 Dec 2013 11:51:53 
To: Kjell Karlsen<la2ni at online.no>
Reply-To: getpri at t-online.de
Cc: <hpsdr at lists.openhpsdr.org>; a.groff<k0vm at mchsi.com>; <K0VM at arrl.net>
Subject: Re: [hpsdr] Re Munin low output on 6m

***** High Performance Software Defined Radio Discussion List *****

Hi Al,

for caps C25 C26 C27 I am using 
- one 479pf 5% 1kV AVX Multilayer ceramic capacitor
- one mica (glimmer) 200pF 5% and
- one mica 100 pF 5%

With these components the output is about 120W - 130W on all bands.

For L4 I tried various constructions.I expected that the version with a
coax-screen as primary coil and teflon cable as secondary coil will be
the best, because of less stray magnetic field. But the best is the one
with 25 Ohm coax cable. 

73, Georg, dl2kp

Am Freitag, den 29.11.2013, 10:52 +0100 schrieb Kjell Karlsen:
> ***** High Performance Software Defined Radio Discussion List *****
> 
> Hi Al.
> 
> Back from holiday in Spain and today I tried to measure the output  
> transformer using practically the same wire as you. With the 4 220 pF  
> capacitors in place I find the compensation too high for 50 MHz so your  
> findings are very strange. I get the best compensation using 660 pF. If  
> this is correct in "real life" has to be checked with a complete Munin.
> 
> Are you sure the capacitors are 220 pF? Can you measure the value of the  
> capacitors?
> 
> I have to do a test to find the exact value of the compensation.  
> Unfortunately I do not have a complete unit so I have to build one. I´ll  
> come back as soon as possible.
> 
> 73, Kjell
> 
> 
> 
> 
> 
> 
> 
> På Fri, 22 Nov 2013 20:40:48 +0100, skrev Kjell Karlsen <la2ni at online.no>:
> 
> > ***** High Performance Software Defined Radio Discussion List *****
> >
> > Hi Al.
> >
> > It seems as if the compensation of the output transformer might be  
> > different with the type of wire you have used compared with what I used.  
> > You may try to remove one of the capacitors and try again to see if it  
> > is worse or better.
> >
> > Can you please measure the wire diameter and the outer diameter of the  
> > insulation.
> >
> > I´ll test with the VNA when I come home next week. At the moment I am in  
> > Spain for a short holiday.
> >
> > 73, Kjell
> >
> >
> >
> >
> >
> > På Fri, 22 Nov 2013 17:50:09 +0100, skrev a.groff <k0vm at mchsi.com>:
> >
> >> Kjell,
> >>     Replacing the Capacitors and I can now get 115 watt at 50mhz and a  
> >> bit more at 53mhz.
> >>
> >>     However, at 28mhz I can only get 90 watts and less at  30mhz .. ( a  
> >> lot less at 42 mhz ).
> >> It appears to start going into saturation at about 75 watt at 28mhz.    
> >> ( I had 100+w at 28 before replacing the capacitors.)
> >>
> >>    I think I shall try tightening up the turns on L4  (??? ) if your  
> >> think that would help.
> >>
> >> AL, K0VM
> >>
> >>
> >>
> >>
> >> On 11/16/2013 11:04 AM, a.groff wrote:
> >>> Kjell,
> >>>    I have the Caps on order and will report back..
> >>>    If the problem is in the final output transformer shouldn't the  
> >>> t1-2 source current increase as driver is increased above saturation ??
> >>>    At 40watts output ( below saturation ) the drive required for 40  
> >>> watts out is basically flat from 160m thru 6m.
> >>>
> >>> AL, K0VM
> >>>
> >>>
> >>> On 11/16/2013 3:30 AM, Kjell Karlsen wrote:
> >>>> Hi Al.
> >>>>
> >>>> I agree that the problem might be one of the capacitors. All my  
> >>>> problems with low power on 6 meter has been with the output  
> >>>> transformer and components around it.
> >>>>
> >>>> Please report back when you have tested with new capacitors.
> >>>>
> >>>> 73, Kjell
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>
> >>>> På Sat, 16 Nov 2013 00:33:28 +0100, skrev Bob Campbell  
> >>>> <joan-bob at bigpond.net.au>:
> >>>>
> >>>>> ***** High Performance Software Defined Radio Discussion List *****
> >>>>>
> >>>>> Hi Al,
> >>>>>
> >>>>> Check caps C25 C26 C27 are all ok.
> >>>>>
> >>>>> Mine failed when I went to load it up on 6m, blew the cermic cap  
> >>>>> apart.
> >>>>>
> >>>>> As Kjell suggested in a previous post replace these caps with four  
> >>>>> 220pf
> >>>>> 500vw 1206 caps.  Since doing this mine has been ok.  I suspect with
> >>>>> this mod the current is shared evenly between all 4 caps and the  
> >>>>> circuit
> >>>>> is much more stable and I have no trouble getting the desired output  
> >>>>> on
> >>>>> 6m now.
> >>>>>
> >>>>> 73's
> >>>>> Bob.c
> >>>>> Vk4xv
> >>>>>
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> >>>>>
> >>>>
> >>>>
> >>>
> >>>
> >>
> >>
> >
> >
> 
> 

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