On Thu, Jan 25, 2018 at 01:20 pm, David wrote:

Instead of whistling into the mic when using an antenna tuner on SSB, we could easily add a tone generator and switch to do that for us. Thoughts?

I have fitted a switchable -6db pad between the output of the pcb and the anttena socket. With the circuit switched in the worst case swr is about 1.65 to 1 with an open or short circuit, this prevents the finals from ever seeing a poor swr. tune is easily achived with the key down and reduced radiated power when tunning up. I use 2 watt carbon resistors 33 ohms in a t attenuator circuit. 2 in parrarlel to give 16.5 ohms which is close enough to the callculated value. I use a relay to switch this attenuator in and out.

You could always use this so you could have built in swr/rf out on your bitx the 51ohm resistors I use 2x 100 ohm 3watt I picked this up from the internet 

On 27 Jan 2018 09:32, "gw4akz via Groups.Io" <gw4akz=aol.com@groups.io> wrote:

On Thu, Jan 25, 2018 at 01:20 pm, David wrote:

Instead of whistling into the mic when using an antenna tuner on SSB, we could easily add a tone generator and switch to do that for us. Thoughts?

I have fitted a switchable -6db pad between the output of the pcb and the anttena socket. With the circuit switched in the worst case swr is about 1.65 to 1 with an open or short circuit, this prevents the finals from ever seeing a poor swr. tune is easily achived with the key down and reduced radiated power when tunning up. I use 2 watt carbon resistors 33 ohms in a t attenuator circuit. 2 in parrarlel to give 16.5 ohms which is close enough to the callculated value. I use a relay to switch this attenuator in and out.

Got a shipping confirmation last night for my December 15 order. Better start working on the case!

If you paid with PayPal, PayPal will notify you when it ships.

Always better to pay the DHL extra as it's fully tracked.

On Jan 27, 2018 7:53 AM, "Arvo KD9HLC via Groups.Io" <arvopl=yahoo.com@groups.io> wrote:

Got a shipping confirmation last night for my December 15 order. Better start working on the case!

I don’t think it’s so much a matter of if they will work or not.  Both will work fine at 50 MHz (and above actually)… the issue is that the RD15HVF1 is a little flatter across the spectrum and from that perspective easier to design around and match.  I use them all the time and they are very easy parts to make work.  A pair will easily put out 30 watts 1-54 MHz if the rest of the design is correct.

 

I’ve been thinking about and have had requests for a nice linear amplifier for the uBITx and these parts are cheap enough to use for that purpose too.  I originally designed one using two RD70HVF1 parts but the cheapest I’ve found them is $18 each.  Not a show stopper but the little brothers are cheaper.  If The parts were under $15 in large quantity, it would be a no brainer.  The auto tuner must be finished first though.  Oh, did I mention, the RD series devices are real RF transistors?

 

 

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

 

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

 

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com

Like us on Facebook!

 

 

email:  bill@...

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of Lawrence Galea
Sent: Saturday, January 27, 2018 3:34 AM

To: BITX20@groups.io
Subject: Re: [BITX20] IRF510 amplifier failures

 

Good morning.

I was thinking about the RD15HVF1 so that it would be easier for people who want to try 50MHz and perhaps 70MHs where available with suitable mods to the μbitx.

 

The RD16HHF1 appears to be  used in the Ukraine transverters as a PA in the 50MHz, 70MHz and 144 MHz transverters while the RD15HBF1 appears to be used in the 222MHz and 432MHz transverters. http://transverters-store.com/50mhz.htm

I have the 50MHz and 70MHz transverters and they do work.
Two years ago I worked more than 40 stations on 70MHz (see my log on QRZ dot com) with a simple dipole at about 4M high on the roof fed with some 50 feet of RG58 coax.

Last year I built a 5 element LFA Yagi for 70MHz but didn't have time to get on the air. 

Lots of data at http://www.g0ksc.co.uk/intro-lfa.html

Regards

Lawrence

 

On Sat, Jan 27, 2018 at 3:41 AM, James Lawrie <lawriejk@...> wrote:

Hello,

 

That’s why I bought 10 ea... for the uBitxs I’ll probably get the others rated at over 30 MHz. Always nice to stock up on useful parts. Out of all listed on there website what would you recommend for HF/VHF use?

James Lawrie

On Jan 26, 2018, at 19:56, K9HZ <bill@...> wrote:

The RD15HVF1 has a bit of a flatter input capacitance curve with frequency so its easier to keep constant gain over 1-54 MHz… but the RD16HHF1 is certainly a worthy part too.  Oh, did I mention, they are both real RF transistors?

 

 

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

 

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

 

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com

Like us on Facebook! <image001.gif>

 

 

email:  bill@...

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of James Lawrie
Sent: Friday, January 26, 2018 2:01 PM
To: BITX20@groups.io
Subject: Re: [BITX20] IRF510 amplifier failures

 

On same site I found these, made for 30 MHz RD16HHF1. Sooo I bought 10 of them, plan to try in Bix40 first. Data sheet even shows a reference amp design, and they are 12 volt like the other one. If it works I’ll let everyone know.

 

James Lawrie

On Jan 26, 2018, at 11:32, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:

The RD15HVF1's should be operated at not much more than 12v.
At 12v, the IRF510's would survive just fine with no antenna connected.
That's an infinite VSWR.

So not obvious that this is a solution to blown FET's.
Though I do think the the Ids curves go up more slowly as Vgs increases on the RD15HF1's,
which makes RV2,RV3 not so touchy.
And the RD15HF1's might be easier to drive at 30mhz.
If you do swap them in, let us know how much power you get at 30mhz.

Jerry, KE7ER

On Fri, Jan 26, 2018 at 03:54 am, KD8CGH wrote:

Wouldn't it be better to change to a RD15HVF1 for high VSWR

 

I am experiencing the same issue. I see no needle movement on the power meter but i get heard on a nearby receiver.

i have changed seceral times the transistors just in case. The same results 

Hi Joe, 
I'm experiencing similar symptoms as captured here: https://groups.io/g/BITX20/topic/7878333?p=Created,,,20,1,40,0 

Current draw indicates that it's making power, but nothing is making it to the antenna. FWIW, my initial bias current was 380 mA. 
 
I validated with a separate receiver that the radio is transmitting. I had concluded that K3 was bad; replaced it tonight (it did measure with open coils), but still no output.  

Tomorrow, I'll follow Ashhar's suggestions in this thread to check around the toroids and I'll run some DC checks on the relay paths. 

--
Dave Beal
AE6RQ