Date   
Re: Substitutions or Sourcing components

Hans Summers <Hans.Summers@...>
 

Ok Mark, I'll wait a few days to see if anyone else wants to be included.
For the benefit of new members who mightn't have read my post the other day:
I have an account with Rapid Electronics and will pass on at cost price: 10x
10MHz crystals, 25x BC547B, 1x IRF510. Cost £6.21 incl UK postage (overseas
postage extra, at cost).

72/3 Hans G0UPL
http://www.hanssummers.com

-----Original Message-----
From: Mark Jones <Mark@...>
To: BITX20@... <BITX20@...>
Sent: Sat Jun 19 08:26:02 2004
Subject: RE: [BITX20] Substitutions or Sourcing components

Hi Hans

Happy to go for a 6.21 order from you!

Regards,

Mark G0MGX

-----Original Message-----
From: Hans Summers [mailto:Hans.Summers@...]
Sent: 18 June 2004 11:56
To: 'BITX20@...'
Subject: RE: [BITX20] Substitutions or Sourcing components



Keytronics has 10MHz xtals at £1.00 each (ten required)
and the 2N3866 seems to be obsolete. Do others see any
difficulties in sourcing parts.
I'm confused about the 2N3866 - what's it for? I see no mention on the
circuit diagram; the nice thing is that a variety of transistors will do in
this design.

Rapid Electronics ( http://www.rapidelectronics.co.uk) sell 10MHz crystals
at
£0.38 each (£0.45 incl sales tax). That drops to £0.305 (£0.36 incl VAT) for
QTY 25+. If enough people want them I'd be happy to order a batch and parcel
them out. People who are interested in 10, let me know within the next few
days and maybe we'll sort it out sometime next week. Assuming 25+, the price
would be £3.86 for 10 including a 1st class UK postage stamp (overseas
postage stamp, extra).

Ok look, I'm not going into the kit business but while we're at it, if you
want them (also from Rapid):

25 BC547B's suitable for the rig: £0.82 incl VAT
1 IRF510: £1.53 incl VAT

Presumably the total weight will be under 60g so these will all fit under
the same single £0.28 postage stamp.

So, for a LIMITED TIME ONLY... Crystals, transistors and the MOSFET, £6.21
incl UK postage (overseas is fine, we just add the extra postage).

72/3 Hans G0UPL
http://www.HansSummers.com



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hans generous offer

wiimford <ford1@...>
 

HI everyone, got an urge to return to homebrew,This looks a good
restarter project. posted an order direct to you Hans.Thanks. Jack

new pictures

ashhar_farhan <farhan@...>
 

i have posted some pictures of the rig that were in my mailbox.
three of them are from hans, from andy.

- farhan

Re: Substitutions or Sourcing components

Jon Harris <jon@...>
 

Sign me up too Hans, where do i send the cash!

Cheers,

Jon H.

----- Original Message -----
From: "Mark Jones" <Mark@...>
To: <BITX20@...>
Sent: Saturday, June 19, 2004 8:26 AM
Subject: RE: [BITX20] Substitutions or Sourcing components


Hi Hans

Happy to go for a 6.21 order from you!

Regards,

Mark G0MGX

-----Original Message-----
From: Hans Summers [mailto:Hans.Summers@...]
Sent: 18 June 2004 11:56
To: 'BITX20@...'
Subject: RE: [BITX20] Substitutions or Sourcing components



Keytronics has 10MHz xtals at �1.00 each (ten required)
and the 2N3866 seems to be obsolete. Do others see any
difficulties in sourcing parts.
I'm confused about the 2N3866 - what's it for? I see no mention
on the
circuit diagram; the nice thing is that a variety of transistors
will do in
this design.

Rapid Electronics (http://www.rapidelectronics.co.uk) sell 10MHz
crystals at
�0.38 each (�0.45 incl sales tax). That drops to �0.305 (�0.36
incl VAT) for
QTY 25+. If enough people want them I'd be happy to order a batch
and parcel
them out. People who are interested in 10, let me know within the
next few
days and maybe we'll sort it out sometime next week. Assuming
25+, the price
would be �3.86 for 10 including a 1st class UK postage stamp
(overseas
postage stamp, extra).

Ok look, I'm not going into the kit business but while we're at
it, if you
want them (also from Rapid):

25 BC547B's suitable for the rig: �0.82 incl VAT
1 IRF510: �1.53 incl VAT

Presumably the total weight will be under 60g so these will all
fit under
the same single �0.28 postage stamp.

So, for a LIMITED TIME ONLY... Crystals, transistors and the
MOSFET, �6.21
incl UK postage (overseas is fine, we just add the extra
postage).

72/3 Hans G0UPL
http://www.HansSummers.com


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oups/S=1705063108:HM/EXP=1087642550/A=2128215/R=0/SIG=10se96mf6/*
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Re: Fw: First QSO with the BITX20 Transceiver

Ashhar Farhan <farhan@...>
 

dear pete,

very good on your efforts. which crystals are you using? the Cb crysals
available for 9MHz are quite cheap. i am using a PC-based AGC system with
some kind of noise blanker and even squelch. it work smuch better than
analog systems. i will post the program soon.

can you resend the pcitures pse? guys on the group would love to see the
pics. send it to me on this email of mine. i am cross posting this to the
BITX group for others to know of your excellent success.

- farhan

On Sat, 19 Jun 2004, Pete Juliano wrote:



Hi Ashhar,

I sent you a series of photos to the phonestock email. I don't think hotmail likes big photo files.

Have now had about 5 QSO's with the rig and have made a few modifications.

For my crystals which are 9.0 MHz --seems like 100PF works best for all capacitors. That made the audio sound better. I also tried substituting a commercial 9.0 Mhz filter in the radio and while there was some improvement --the homebrew filter is quite good.

I added a small 25K pot as a mic gain control. seems like I could overdrive the radio with the microphone I am using.

I also had to add a second relay. There is a dpdt relay at the linear board just like on the schematic. However I was getting stray RF feedback --so I added a second spst relay right at the bandpass network on the mainboard-- now there is no rf feedback.

Have you given any thought to adding a simple AGC system. Loud stations really play havoc on receive -- some sort of system to change the bias level on the Rcv IF amp might be easy to implement.

I hope to get it in a metal box this next week.

Thanks again for such a neat project.

Re: Substitutions or Sourcing components

Ashhar Farhan <farhan@...>
 

i am in delhi and i iaccidentally discovered the outlet of a major
manufacturer of those tv balun cores. i have bought 500 of them for Rs.200
(about 4 dollars). sending it across to england and usa is a bit of a
problem. i will find someone to carry them to these countries and post it
to some of you.

the shop might ship them abroad but the shipping costs from here are
prohibitive. if only the qsl bureaus also handled components!

- fahran

On Sat, 19 Jun 2004, Jon Harris wrote:

Sign me up too Hans, where do i send the cash!

Cheers,

Jon H.

----- Original Message -----
From: "Mark Jones" <Mark@...>
To: <BITX20@...>
Sent: Saturday, June 19, 2004 8:26 AM
Subject: RE: [BITX20] Substitutions or Sourcing components


Hi Hans

Happy to go for a 6.21 order from you!

Regards,

Mark G0MGX

-----Original Message-----
From: Hans Summers [mailto:Hans.Summers@...]
Sent: 18 June 2004 11:56
To: 'BITX20@...'
Subject: RE: [BITX20] Substitutions or Sourcing components



Keytronics has 10MHz xtals at �1.00 each (ten required)
and the 2N3866 seems to be obsolete. Do others see any
difficulties in sourcing parts.
I'm confused about the 2N3866 - what's it for? I see no mention
on the
circuit diagram; the nice thing is that a variety of transistors
will do in
this design.

Rapid Electronics (http://www.rapidelectronics.co.uk) sell 10MHz
crystals at
�0.38 each (�0.45 incl sales tax). That drops to �0.305 (�0.36
incl VAT) for
QTY 25+. If enough people want them I'd be happy to order a batch
and parcel
them out. People who are interested in 10, let me know within the
next few
days and maybe we'll sort it out sometime next week. Assuming
25+, the price
would be �3.86 for 10 including a 1st class UK postage stamp
(overseas
postage stamp, extra).

Ok look, I'm not going into the kit business but while we're at
it, if you
want them (also from Rapid):

25 BC547B's suitable for the rig: �0.82 incl VAT
1 IRF510: �1.53 incl VAT

Presumably the total weight will be under 60g so these will all
fit under
the same single �0.28 postage stamp.

So, for a LIMITED TIME ONLY... Crystals, transistors and the
MOSFET, �6.21
incl UK postage (overseas is fine, we just add the extra
postage).

72/3 Hans G0UPL
http://www.HansSummers.com


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oups/S=1705063108:HM/EXP=1087642550/A=2128215/R=0/SIG=10se96mf6/*
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Re: Substitutions or Sourcing components

Hans Summers <Hans.Summers@...>
 

Please, do not send me any money yet! Now I have 6 orders, which takes us to
the 100+ pricing for the BC547B so everything will become slightly cheaper.
Thanks for your emails, I will reply individually as soon as I get the
chance, which probably won't be until Monday.

It's nice to see so many people joining this group and planning to build
this neat design.

I'm happy to extend my offer of bulk purchase components from Rapid
Electronics to optionally include for those who want them, some of the other
parts which you might not find so easily in your junk boxes. I'm thinking of
the 9V1 and 36V zener diodes, 7805 voltage regulator, 10x 1N4148 diodes,
trimmer capacitors, and possibly something to substitute the 2N2218 driver
transistor. All small components which won't much increase the weight, and
will still mean I can use small envelopes and not worry about special
packaging etc. I'll work out prices on Monday at my office, which is where
my Rapid Electronics catalogue resides ;-)

In his prior version Farhan was using two BC547 parallelled, and only
replaced them with a single heatsinked 2N2218 when the '547's were fried
during a long PSK31 QSO. Can Farhan or anybody else suggest alternatives
since I don't think Rapid sell the 2N2218?

Now a word about the crystals. Farhan recommends buying 10 and choosing the
closest 4 for the filter. I did so and chose the next closest one for the
BFO though this wouldn't really be critical. Measurement could be via a
frequency counter or zero beating on another receiver with digital readout
and coverage of 10MHz. I have a homebrewed counter in my HF receiver, you
can read about it on my webpage. But if you don't have either of those items
I can imagine a rather simple and cheap frequency counter circuit having
only 3 common 74HC-series IC's and a handful of LED's for binary readout of
frequency, providing more than sufficient resolution for the task. Failing
all of that I'd seriously suggest getting just 5 crystals and trying them
anyway. When I measured my 10 they were quite close and I think reasonable
results would be obtainable without the precise matching if suitable
equipment isn't available. I'm interested in other people's opinion on this.
If I can manage to find my notes on Monday I'll post my ten measurements,
and you'll see what I mean.

Any more orders, let me know via email. But remember, no money yet until I
make final calculations.

72/3 Hans G0UPL
http://www.hanssummers.com

-----Original Message-----
From: Jon Harris <jon@...>
To: BITX20@... <BITX20@...>
Sent: Sat Jun 19 22:25:36 2004
Subject: Re: [BITX20] Substitutions or Sourcing components

Sign me up too Hans, where do i send the cash!

Cheers,

Jon H.

----- Original Message -----
From: "Mark Jones" <Mark@...>
To: <BITX20@...>
Sent: Saturday, June 19, 2004 8:26 AM
Subject: RE: [BITX20] Substitutions or Sourcing components


Hi Hans

Happy to go for a 6.21 order from you!

Regards,

Mark G0MGX

-----Original Message-----
From: Hans Summers [mailto:Hans.Summers@...]
Sent: 18 June 2004 11:56
To: 'BITX20@...'
Subject: RE: [BITX20] Substitutions or Sourcing components



Keytronics has 10MHz xtals at £1.00 each (ten required)
and the 2N3866 seems to be obsolete. Do others see any
difficulties in sourcing parts.
I'm confused about the 2N3866 - what's it for? I see no mention
on the
circuit diagram; the nice thing is that a variety of transistors
will do in
this design.

Rapid Electronics (http://www.rapidelectronics.co.uk) sell 10MHz
crystals at
£0.38 each (£0.45 incl sales tax). That drops to £0.305 (£0.36
incl VAT) for
QTY 25+. If enough people want them I'd be happy to order a batch
and parcel
them out. People who are interested in 10, let me know within the
next few
days and maybe we'll sort it out sometime next week. Assuming
25+, the price
would be £3.86 for 10 including a 1st class UK postage stamp
(overseas
postage stamp, extra).

Ok look, I'm not going into the kit business but while we're at
it, if you
want them (also from Rapid):

25 BC547B's suitable for the rig: £0.82 incl VAT
1 IRF510: £1.53 incl VAT

Presumably the total weight will be under 60g so these will all
fit under
the same single £0.28 postage stamp.

So, for a LIMITED TIME ONLY... Crystals, transistors and the
MOSFET, £6.21
incl UK postage (overseas is fine, we just add the extra
postage).

72/3 Hans G0UPL
http://www.HansSummers.com


Yahoo! Groups Sponsor

ADVERTISEMENT

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oups/S=1705063108:HM/EXP=1087642550/A=2128215/R=0/SIG=10se96mf6/*
http://comp
anion.yahoo.com> click here

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Re: Substitutions or Sourcing components

Hans Summers <Hans.Summers@...>
 

Jon, I'll send you an email tomorrow with final details. 72/3 de Hans G0UPL

-----Original Message-----
From: Jon Harris <jon@...>
To: BITX20@... <BITX20@...>
Sent: Sat Jun 19 22:25:36 2004
Subject: Re: [BITX20] Substitutions or Sourcing components

Sign me up too Hans, where do i send the cash!

Cheers,

Jon H.

----- Original Message -----
From: "Mark Jones" <Mark@...>
To: <BITX20@...>
Sent: Saturday, June 19, 2004 8:26 AM
Subject: RE: [BITX20] Substitutions or Sourcing components


Hi Hans

Happy to go for a 6.21 order from you!

Regards,

Mark G0MGX

-----Original Message-----
From: Hans Summers [mailto:Hans.Summers@...]
Sent: 18 June 2004 11:56
To: 'BITX20@...'
Subject: RE: [BITX20] Substitutions or Sourcing components



Keytronics has 10MHz xtals at £1.00 each (ten required)
and the 2N3866 seems to be obsolete. Do others see any
difficulties in sourcing parts.
I'm confused about the 2N3866 - what's it for? I see no mention
on the
circuit diagram; the nice thing is that a variety of transistors
will do in
this design.

Rapid Electronics (http://www.rapidelectronics.co.uk) sell 10MHz
crystals at
£0.38 each (£0.45 incl sales tax). That drops to £0.305 (£0.36
incl VAT) for
QTY 25+. If enough people want them I'd be happy to order a batch
and parcel
them out. People who are interested in 10, let me know within the
next few
days and maybe we'll sort it out sometime next week. Assuming
25+, the price
would be £3.86 for 10 including a 1st class UK postage stamp
(overseas
postage stamp, extra).

Ok look, I'm not going into the kit business but while we're at
it, if you
want them (also from Rapid):

25 BC547B's suitable for the rig: £0.82 incl VAT
1 IRF510: £1.53 incl VAT

Presumably the total weight will be under 60g so these will all
fit under
the same single £0.28 postage stamp.

So, for a LIMITED TIME ONLY... Crystals, transistors and the
MOSFET, £6.21
incl UK postage (overseas is fine, we just add the extra
postage).

72/3 Hans G0UPL
http://www.HansSummers.com


Yahoo! Groups Sponsor

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001176/D=gr
oups/S=1705063108:HM/EXP=1087642550/A=2128215/R=0/SIG=10se96mf6/*
http://comp
anion.yahoo.com> click here

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D=groups/S=
:HM/A=2128215/rand=403314333>


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We're off and running!

Mark <Mark@...>
 

Hi All

I've completed the VFO today, some pictures on the reflector.

Just need to wait for Hans Components Inc before we go any further.

VFO swinging from 4.25MHz to 4.4MHz - very adjustable with the
trimmer.

I used a fixed inductor of 22uH instead of the tap washer and 150
turns of 32swg - can't count that high.

What are other people planning for inductor cores - is the general
plan to proceed with tap washers or has anyone done the calcs for
more conventional cores?

Your comments welcome.

Mark G0MGX

Re: Fw: First QSO with the BITX20 Transceiver (fwd)

Ashhar Farhan <farhan@...>
 

---------- Forwarded message ----------
Date: Sat, 19 Jun 2004 22:08:39 -0700
From: Pete Juliano <jessystems@...>
To: Ashhar Farhan <farhan@...>
Subject: Re: Fw: First QSO with the BITX20 Transceiver


Hi Ashhar,

For the crystal filter I am using 9.0 MHz computer crystals. I built a test oscillator and measured them with a frequency counter. Out of a group of 20, I found 4 that were within 50 hertz of each other. Those are the four in the radio. When I jumpered in a Commercial Filter to make a comparison, I didn't even have to touch up the carrier oscillator crystal so the HB filter has a very close center frequency to the commercial unit. The HB Filter does a nice job and is cheap --20 crystals cost me about $7 USD and within that remainder is another batch that could be used for a second filter.

Attached are several photos of my version of the BITX20 including the Linear Amp, an overall view of the boards with digital display and a close up of the main circuit board. Hopefully next week I will have it all in a box. The VFO and stabilizer are as large as the mainboard. I used sockets for all of the semiconductors so I could do a little testing of various transistors and IC's

The linear amp output filter has the following constants. 220PF, L1 which is 12 Turns of # 26SWG on an FT37-2 powdered iron core form (red core ~ 0.55 uhy). Then followed by a 220PF in parallel with a 330 PF (= 550 PF) followed by L2 same as L1 and then a 220 PF. The caps are ceramic on glass and rated at 100 volts. Really small caps. I used a 78L05 regulator and the bias adjust --I used what I had --a 25K ohm pot in parallel with a22K ohm resistor. Works fine. The linear amp board is 2inches X 2 inches (5CM X 5CM).

You will note two relays --one at the linear amp just like the schematic --but I also had to resort to a relay at the main board as there was a RF feedback problem. The second relay solved that problem.

The microphone is a low impedance --A D104 (lollipop) fitted with a Heil HC4 cartridge. I have a 25K ohm pot soldered right at mic connector and use that to set the mic gain.


The last two evenings 20 meters has been hot and the RX is doing a FB job. Despite my initial comments about receiver sensitivity it is more than adequate.

If I get a chance I may try my hand at an analog agc circuit.

Again a very nice radio and despite its subtle simplicity --it packs a lot of peformance.

I will keep you posted on my progress.

73's
Pete W6JFR

Sunday

david.g3ryp <david.g3ryp@...>
 

I wonder how much output everyone's getting from the IRF510?
 
I can get 2.5 watts rf maximum but this drops to well under a watt with the lpf in circuit. I've checked the lpf cut-off and I would expect some attenuation but not that much. I tried an irf530 which promptly overheated and destroyed itself as I increased the bias!
 
I'm hopeless when it comes to getting rf out of solid state stuff!
 
David

Re: We're off and running!

Hans Summers <Hans.Summers@...>
 

Now the heat's really on at Hans Compoments Inc, then ;-)

I used the tap washers for the inductors. Mine are a black rubbery type of
material, I didn't find white nylon ones like Farhan's photos. It was fun to
do things a bit "differently". I was not finding it so fun in the middle of
150 turns on the VFO coil but proud of the result when I'd finished.

http://www.gqrp.com the GQRP club sell the FT37-43 toroidal cores which I
used as per Farhan's recommendation in place of TV baluns. Club sales are
for members only, £0.75 per pack of 5 and they sell all the normal types
too. There are calculators and toroid inductance charts all over the
internet, a google search will find one immediately. I wonder if temperature
stability will be better in the case of the tap washers than a ferrite core?

72/3 de Hans G0UPL
http://www.hanssummers.com

-----Original Message-----
From: Mark <Mark@...>
To: BITX20@... <BITX20@...>
Sent: Sun Jun 20 13:19:36 2004
Subject: [BITX20] We're off and running!

Hi All

I've completed the VFO today, some pictures on the reflector.

Just need to wait for Hans Components Inc before we go any further.

VFO swinging from 4.25MHz to 4.4MHz - very adjustable with the
trimmer.

I used a fixed inductor of 22uH instead of the tap washer and 150
turns of 32swg - can't count that high.

What are other people planning for inductor cores - is the general
plan to proceed with tap washers or has anyone done the calcs for
more conventional cores?

Your comments welcome.

Mark G0MGX





Yahoo! Groups Links

What are tap washers ?

Heinz Schnait <oe5eep@...>
 

Please could somebody explain to a non-native speaker what "tap washers"
are and where to source them?

I guess this must be some sort of "plastic toroid" (ab)used as a coil former.
But what is its original use?

Heinz, OE5EEP

Re: What are tap washers ?

Mark Jones <Mark@...>
 

Hmm, good question. An American asked me recently what a "jubilee clip" was - that was a struggle.
 
A tap washer is a thin shim of rubber/nylon/fibre that fits inside a water tap (faucet?) - like in the bathroom - so that when the water valve is closed there are no leaks.
 
Does this help at all?
 
If this doesn't help and you need some pictures of tap washers I can take some and upload to the reflector for you.
 
Maybe we need a photo album called "what is a tap washer"
 
Mark. G0MGX

-----Original Message-----
From: Heinz Schnait [mailto:oe5eep@...]
Sent: 20 June 2004 15:04
To: BITX20@...
Subject: [BITX20] What are tap washers ?

Please could somebody explain to a non-native speaker what "tap washers"
are and where to source them? 

I guess this must be some sort of "plastic toroid" (ab)used as a coil former.
But what is its original use?

Heinz, OE5EEP


Re: Substitutions or Sourcing components

Jon Harris <jon@...>
 

Thanks Hans, and many thanks for the offer of help, much
appreciated!

73,

Jon H.

----- Original Message -----
From: "Hans Summers" <Hans.Summers@...>
To: <BITX20@...>
Sent: Sunday, June 20, 2004 10:28 AM
Subject: Re: [BITX20] Substitutions or Sourcing components



Jon, I'll send you an email tomorrow with final details. 72/3 de
Hans G0UPL


-----Original Message-----
From: Jon Harris <jon@...>
To: BITX20@... <BITX20@...>
Sent: Sat Jun 19 22:25:36 2004
Subject: Re: [BITX20] Substitutions or Sourcing components

Sign me up too Hans, where do i send the cash!

Cheers,

Jon H.

----- Original Message -----
From: "Mark Jones" <Mark@...>
To: <BITX20@...>
Sent: Saturday, June 19, 2004 8:26 AM
Subject: RE: [BITX20] Substitutions or Sourcing components


Hi Hans

Happy to go for a 6.21 order from you!

Regards,

Mark G0MGX

-----Original Message-----
From: Hans Summers [mailto:Hans.Summers@...]
Sent: 18 June 2004 11:56
To: 'BITX20@...'
Subject: RE: [BITX20] Substitutions or Sourcing components



Keytronics has 10MHz xtals at �1.00 each (ten required)
and the 2N3866 seems to be obsolete. Do others see any
difficulties in sourcing parts.
I'm confused about the 2N3866 - what's it for? I see no mention
on the
circuit diagram; the nice thing is that a variety of transistors
will do in
this design.

Rapid Electronics (http://www.rapidelectronics.co.uk) sell 10MHz
crystals at
�0.38 each (�0.45 incl sales tax). That drops to �0.305 (�0.36
incl VAT) for
QTY 25+. If enough people want them I'd be happy to order a batch
and parcel
them out. People who are interested in 10, let me know within the
next few
days and maybe we'll sort it out sometime next week. Assuming
25+, the price
would be �3.86 for 10 including a 1st class UK postage stamp
(overseas
postage stamp, extra).

Ok look, I'm not going into the kit business but while we're at
it, if you
want them (also from Rapid):

25 BC547B's suitable for the rig: �0.82 incl VAT
1 IRF510: �1.53 incl VAT

Presumably the total weight will be under 60g so these will all
fit under
the same single �0.28 postage stamp.

So, for a LIMITED TIME ONLY... Crystals, transistors and the
MOSFET, �6.21
incl UK postage (overseas is fine, we just add the extra
postage).

72/3 Hans G0UPL
http://www.HansSummers.com


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Re: Low Output (was Sunday)

ashhar_farhan <farhan@...>
 

--- In BITX20@..., "david.g3ryp" <david.g3ryp@n...>
wrote:
I wonder how much output everyone's getting from the IRF510?

I can get 2.5 watts rf maximum but this drops to well under a watt
with the lpf in circuit. I've checked the lpf cut-off and I would
expect some attenuation but not that much. I tried an irf530 which
promptly overheated and destroyed itself as I increased the bias!

I'm hopeless when it comes to getting rf out of solid state stuff!

David
hehe, david worry not. there are a couple of things that you ought
to check.
1) cut the supply to the IRF510. then measure the RF output of the
driver at 50 ohms resistors across the RIF510's gate. it should show
5 volts peak (that is 10 volts between the +ve and -ve swing). If
you not are getting that much, then you have probably wired the
output
transformer incorrectly. they are probably in parallel to each
other, or worse, the
drain and the power supply are connected to the separate ends of the
winding. check it carefully.

2) if you are not getting 5 volts at the 50 ohms resistor across the
IRF510, then measure the output from the predriver. it should be a
more than one volt peak (2 volts peak to peak on the 'scope). if
either of these is a problem. check the following:

a)that the collectors are showing somewhere north of 10 volts and
the emitters are showing about 2 volts on both the driver and the
predriver.

b)if the DC voltages are alright, suspect that the AC connections
are a problem. Most probably it is a mis-wired transformer. take
them out of the circuit and check them carefully. i frequently make
a mistake with shorting the opposite ends of the SAME wire and
leaving the other wire in the pair isolated.d

c) the 6.3 ohms, in my case is approximated by paralleling two 10
ohms. check that the 10 ohms IS 10 ohms and not 100 ohms. it is easy
to confuse brown-black-brown with brown-black-black.

above all, trace! measure the outputs at the RF fitler, pre-driver
and the PA. tell us how much you get at each point. we will 'divide
and conquer'.

i dont know if i mentioned in the article that you should set the
drain current to between 50 and 80mAs. I set it at 80mA, a bit on
the higher side, but the linearity is better.


- farhan

Use 2N3866 instead of 2N2218

Ashhar Farhan <farhan@...>
 

the 2N2218 is a fatter type of 2N2222. you can use the 2N3866 instead.
they are expensive in india. but they might be easier to find elsewhere.

- farhan

On Mon, 21 Jun 2004, Hans Summers wrote:

Rapid do not stock 2N2218 driver transistors, nor are they at Farnell
http://www.Farnell.com. However I have managed to find a different source
for supply of 2N2219A which is like the 2N2218 but has better gain
specification. I'm sure it will be suitable.

Re: linear coil

Ashhar Farhan <farhan@...>
 

On Mon, 21 Jun 2004, jillian swannack wrote:

Hi ashhar, sorry to bother you but, I was wanting to know if 3uH for T5 in the linear amp is across the total winding or from one end to the centre tap. thanks kind regards. mark.
i calculated 3uH on each winding.
- farhan

Low output

david.g3ryp <david.g3ryp@...>
 

Many thanks for the advice Farhan.
 
I've taken the measurements you suggested and indeed it was the driver whose output was low - only about 1 volt peak. I was using BC549s throughout and although they tested ok when I changed them in the pre-driver and driver stages for 2n2369s the output from the driver went up to 4.5volts peak.
 
I've tried a variety of core types and none appears to be critical. I'm using a t-50-6 in the IRF510 drain - 14 bifiliar turns to get the 3uh you suggest. Know what you mean about winding these things!
 
The output without the lpf in circuit is 6.25watts but I need to adjust the bias for a standing current of rather more than 80ma to achieve this - although it may be that the balanced mod is not that well balanced (I haven't put in any caps yet).
I'll test this and let you know. Even without the lpf the output is quite a pretty sine-wave.
 
Now where does this 6.3 volt resistor fit in? Am I looking at the wrong schematic? Perhaps in the driver emitters? I'll try changing the 10 ohms to 5.6 or thereabouts and see if the output goes up.
 
Lastly thanks for putting a unit on the rf voltages. All too often schematics either don't contain rf voltages at all or they don't specify whether they're Peak to Peak or Peak or RMS - and there's quite a difference!
 
I think I'll change the other 549s for 2n2369s if I have enough just to see what happens.
 
Good luck to everyone.
 
David 

Re: Low output

Ashhar Farhan <farhan@...>
 

On Mon, 21 Jun 2004, david.g3ryp wrote:

I've taken the measurements you suggested and indeed it was the driver whose output was low - only about 1 volt peak. I was using BC549s throughout and although they tested ok when I changed them in the pre-driver and driver stages for 2n2369s the output from the driver went up to 4.5volts peak.

I've tried a variety of core types and none appears to be critical. I'm using a t-50-6 in the IRF510 drain - 14 bifiliar turns to get the 3uh you suggest. Know what you mean about winding these things!

The output without the lpf in circuit is 6.25watts but I need to adjust the bias for a standing current of rather more than 80ma to achieve this - although it may be that the balanced mod is not that well balanced (I haven't put in any caps yet).
I'll test this and let you know. Even without the lpf the output is quite a pretty sine-wave.
Now where does this 6.3 volt resistor fit in? Am I looking at the wrong schematic? Perhaps in the driver emitters? I'll try changing the 10 ohms to 5.6 or thereabouts and see if the output goes up.
The driver and prediver's emitter resistors are 6.2ohms (i used 5 ohms).

due to the feedback design, individual transistor types are non-critical.
the driver did require a heavier than BC147/2N3904 type of transistor.
The plastic package prevents one from being able to gauge their heating by
just touching them. until they are properly cooked.

the 2N3866 will do fine. the latest 'build' of the circuit is on
www.phonestack.com/farhan.

- farhan

Lastly thanks for putting a unit on the rf voltages. All too often schematics either don't contain rf voltages at all or they don't specify whether they're Peak to Peak or Peak or RMS - and there's quite a difference!

I think I'll change the other 549s for 2n2369s if I have enough just to see what happens.

Good luck to everyone.

David