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U3S RF Power Transistor

 

Hi all,

has anybody made experiences with substituting the (one) BS170 with a RD06HHF and supplying with 12 V ?

73 DC1MAK micha
 

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Hi Micha,

I tried the IRF510 and the RD15HVF1 FETs on a home made 'dead bug' style PA using the same circuit as the U3S BS170 FET PA with the bifilar wound toroid.? The FET gate was driven via a 0.1uF coupling capacitor by the 3V p-p waveform from a QRP-Labs si5351a synth board.? The bias was set so the FET drew a few mA with no RF drive.?? Both FETs worked fine at 20m and 30m where it was tested.? There was somewhat more power output from the RD15HVF1 than from the IRF510.? The power output from the RD15HVF1 with the PA voltage at 9V was 0.4W on 20m with 170mA drain current,? and 1W on 30m with 230mA of drain current.? I did not record the result with higher drain voltage, but there was considerably more output ... I do remember seeing over 2W with something like 12 or 13V on the FET.?? A heatsink was necessary on the FET ... I used something similar to the one supplied with the QRP-Labs 5W PA kit.

Given that the circuit is the same, similar results could be expected when replacing the BS170 FET in a U3S with a RD06HHF FET although I have not tried that configuration exactly.

73, Bob? ZL1RS


.
 

I put one of those mitsubishi transistors in, feed directly from the site 5351, bolted the transistor to the bottom of the u3 chassis, put the bias potentiometer in one of the front holes of the chassis, using the bifilar transformer, ?I can adjust power from 1.5w to 4 over the whole 3-30MHz span.
 

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Yep. Me too.?


Dr.?William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

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Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

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Owner – Operator

Villa Grand Piton - J68HZ

Soufriere, St. Lucia W.I.

Rent it:


email:??bill@...

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On Sep 8, 2017, at 2:51 PM, Mikael Dagman <mikael_dagman@...> wrote:

I put one of those mitsubishi transistors in, feed directly from the site 5351, bolted the transistor to the bottom of the u3 chassis, put the bias potentiometer in one of the front holes of the chassis, using the bifilar transformer, ?I can adjust power from 1.5w to 4 over the whole 3-30MHz span.

[email protected]
 

Hi Michael,
Thanks for your post on this.

I understand how to replace the standard transistors with the Mitsubishi device. But how did you configure the extra bias pot? Did you simple replace this, or did you place a second pot in series or something like that? How did you avoid over driving the transistor by accident?

Thank you in advance for you advice and comments.
 

I made an RD06HHF external amp, for my QRP Labs rigs and for general use.



I have one of my QRP Labs rigs set for about 200mw output, and pass it via a 3db attenuator.

I prefer to use an attenuator because it keeps the impedance constant at 50R regardless of frequency (RD06HHF is about 200R).

- Andy -
 

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No harmonic filters?

?

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Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

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Moderator – North American QRO Group at Groups.IO.

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email:? bill@...

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From: [email protected] [mailto:[email protected]] On Behalf Of Andy Brilleaux via Groups.Io
Sent: Thursday, April 11, 2019 5:40 AM
To: [email protected]
Subject: Re: [QRPLabs] U3S RF Power Transistor

?

I made an RD06HHF external amp, for my QRP Labs rigs and for general use.



I have one of my QRP Labs rigs set for about 200mw output, and pass it via a 3db attenuator.

I prefer to use an attenuator because it keeps the impedance constant at 50R regardless of frequency (RD06HHF is about 200R).

- Andy -


Virus-free.

 

Hi,

His diagrams point to the low pass filters. Those are so very common they need not be included - merely mentioned. He mentions them:)

73,

Bill KU8H

On 4/11/19 12:12 PM, J68HZ wrote:
No harmonic filters?
**
*Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ*
Moderator – North American QRO Group at Groups.IO.
email: bill@... <mailto:bill@...>
*From:*[email protected] [mailto:[email protected]] *On Behalf Of *Andy Brilleaux via Groups.Io
*Sent:* Thursday, April 11, 2019 5:40 AM
*To:* [email protected]
*Subject:* Re: [QRPLabs] U3S RF Power Transistor
I made an RD06HHF external amp, for my QRP Labs rigs and for general use.

I have one of my QRP Labs rigs set for about 200mw output, and pass it via a 3db attenuator.
I prefer to use an attenuator because it keeps the impedance constant at 50R regardless of frequency (RD06HHF is about 200R).
- Andy -
<> Virus-free. www.avg.com <> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
--
bark less - wag more
 

@c.s.coles
this should clear it


I have U3 kit which I have modified to a U3S so I dont have any bias port on my pcb, but as you might have just remove that and put it somewhere on the chassis for easy adjustment .
 

Here you go. Works great:

--
Best regards,
Chris
M0XFL

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