Date   
Re: CB amplifiers RM-Italy KL203P

Jim Strohm
 

Iz,

If you have questions about solid-state (SS) amp topologies, please know that the RM-Italy amps (as do darn near every HF SS amp ever made since 1970) closely follow the Helge Granberg designs for Motorola, starting about 1968 and continuing well past 2000.

These designs are easy to find on the internet.

But as to your questions, it's difficult to get much more than a decade (e.g., 3 - 30 MHz, or 10X) of bandwidth using the older designs.  To go lower than 3 MHz, you'll need more rust in your ferrites -- that is, larger cores -- in both the input and output, and that tends to limit your high-frequency usability.  Especially w/ those RM-Italy amps.  Just adding a capacitor won't do it -- you can pull the input down in freq., but you'll lose at least the same comparable bandwidth up top.

If you look at the Jerry Sevick (SK) W2FMI books, you'll find some ways to stretch your bandwidth.  They're pretty simple to achieve once you know what you're doing, and not too expensive, but take a great deal of study at first.  And these books aren't cheap.

My recommendation?  Pay somebody who's already mastered the techniques for their expertise and finished products.

I have a few funny stories about making bootleg SS CB amps from the early 1980s.  Based on those experiences, I suggest people BUY these amps new or used, or at least buy dead ones from the ham radio flea market, and then resurrect them. 

Dead ones usually go for about USD$5 or $10, and the parts needed for resurrection are easy to determine, source, and replace.

Yes, you still need lo-pass filters.

73
Jim N6OTQ

Re: No Power

Skip Davis
 

First of all did your UBITX TX when you were using the stock firmware? You haven’t said it worked on both RX and TX after wiring up or did I miss that in your post? If not then possibly you have connected the wires to the wrong pins on the jacks, there are pins that are switched out when a plug is installed. 

Skip Davis, NC9O

On Jun 11, 2018, at 09:27, G8HAV <g8hav@...> wrote:

Hi,
Having built  the uBITZ and been checking receive and all is well. Loaded KD8CEC version 1.8 and checked receive again.

Now tried CW TX but got no power out. Read all the topics on a previous 'No Power' topic and followed all the checks.
All TX voltages are present and the main oscillators must all be running as receive is working well.

Got a simple 10 MHz scope and checked the output from the MIC amp and CW tone to the mixer and I cannot detect any change of signal 
when operating the PTT and the CW key. 

I will wire up a MIC element and test the audio from that later.

Any ideas would be welcome as I am reasonably competent in fault finding; I may make a tone generator and inject a tone into the mixer to check for power out.
There is a CW  tone output on pin 15 which I think is where the Raduino is plugged into the motherboard. 

That's my next check.

Thanks

Re: Transmitter Mods

Dave de WS1ETI <docame12@...>
 

I would be grateful to take advantage of your generosity. Is your address on QRZ good?

Dave, WS1ETI

Re: Latest Build, Mods and results.

Skip Davis
 

Nice looking build Mike I like your enclosure. 

Skip Davis, NC9O

On Jun 11, 2018, at 18:28, Mharpen@... wrote:

Hello, I enjoyed by first build so much I built another one. Avoiding all of the mistakes of the first one. Attached are the photos, below are the mods and results.
TX: 1. Choke in series with R86.
       2. All emitter resistors in buffer, predriver and driver bypassed.
       3. Feedback resistor in PA increased to 600 Ohms.
       4. Output Xformer replace with 2:4 on BN43-202.
       5. Adafruit audio compressor in mic line with chokes to eliminate RF feedback.
       6. PA powered by buck boost at 13.8V the rest of the board by 12V battery.
RESULTS: 30W on 80 and 40, 20W on 20. RV1 adjusted to reduce output to 15W.
RX: 1. ND6T AGC installed (underneath main board) at K3 powered by 5V regulator chip.
       2. Additional stage of audio gain installed between Q70 and U1 to make up for loss due to AGC.
RESULTS: Plenty of audio!! and good AGC action.
       3. VE1BWV audio pop mod (similar to the one standard on the new ubitx) installed underneath the main board.
       4. To further enhance the pop suppression PIN 1 at K3 is grounded.
RESULTS: Sounds fine to me.
Trivial Mods: a red/green LED TX/RX LED is installed on front. A TX/RX relay to key an external PA is installed on the back.
Ya'll have a nice day. Mike N6CMY. 
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Re: Transmitter Mods

Howard Fidel
 

Yes, and I still have enough parts for every uBitx sold.

On 6/11/2018 9:11 PM, Dave de WS1ETI wrote:
I would be grateful to take advantage of your generosity. Is your address on QRZ good?

Dave, WS1ETI


Re: Net Neutrality Ending

Richard Spohn
 

Also agreed. - Rich

On 6/11/18, Bo Barry <wn4ghv@...> wrote:
Agreed. Sorry



Re: Transmitter Mods

Tom Christian
 

Jerry, Fantastic tips!  Will follow up.  I'm keeping your comments in my notes as a great reference.  Wish I'd had that info before I fought (and lost) with R85 on both rigs..... At least the discreat version surrender worked.....:) Thanks!
Tom
AB7WT

Re: RF power chain mods and improvements..

ajparent1/KB1GMX <kb1gmx@...>
 

Nick,

Came though beautifly.   

When you power it up let us know how it works for you.

Thanks!

Allison

Re: RF power chain mods and improvements..

Kees T
 

Hey, that's looking a lot like my robust 12V 20W Amp .....except my output transformer is 1:2 turns ratio with the 1 turn made from copper tubing and the ferrite material is #61 (#43 runs too hot....wastes power).  I think there is also a pony in using a pair of RD06HHF1 MOSFETs for a robust 12V 10W HF Amp with a BN43-202 (couldn't find a BN61-202) with 1:2 turns using coax shield copper for the 1 turn. The single 12V 5W RD06HHF1 Amp uses a 1:3 turns ratio. They all work well on 6m too.

73 Kees K5BCQ 

Re: RF power chain mods and improvements..

Kees T
 

Almost forgot......back when I was testing "many" RF Amp output transformers I came across some handmade binocular cores sold by RF Parts. They are small and appear to work fine ..HOWEVER... a batch I bought had apparently been overheated in the "xyz corp" assembly house and had several of the small ferrite sleeves cracked. So if you go that route, beware. The cracked sleeves "don't work so good".

73 Kees K5BCQ

Re: RF power chain mods and improvements..

Satish Chandorkar
 

It seams that there is sufficient room to stack another T50-43 in the final transformer so as to ease stresses and heating of
the transformer while trying to get maximum output from it

Satish VU2SNK

On Tue, Jun 12, 2018 at 8:42 AM, Kees T <windy10605@...> wrote:
Hey, that's looking a lot like my robust 12V 20W Amp .....except my output transformer is 1:2 turns ratio with the 1 turn made from copper tubing and the ferrite material is #61 (#43 runs too hot....wastes power).  I think there is also a pony in using a pair of RD06HHF1 MOSFETs for a robust 12V 10W HF Amp with a BN43-202 (couldn't find a BN61-202) with 1:2 turns using coax shield copper for the 1 turn. The single 12V 5W RD06HHF1 Amp uses a 1:3 turns ratio. They all work well on 6m too.

73 Kees K5BCQ 


Re: RF power chain mods and improvements..

Nick VK4PP
 

On Mon, Jun 11, 2018 at 08:12 pm, Kees T wrote:
Hey, that's looking a lot like my robust 12V 20W Amp"
"All roads lead to Rome" and "When in Rome" ...

I suppost the end result is to have a PA in the uBITX like your 20W amp.
I had even concidered stripping out everything from RV1 and just installing your 20W amp or the Aussie Minikits 16W amp of similar design...

Good tip on the Output transformer. I used the 202 as it fit well and I really cant detect any heating. Maybe a BN61-202 would be even better... I grab a few in my next parts order.

Whats the difference in doing 1:2 with coax, or like I've done 2:4 with enameled wire?

73 Nick VK4PLN

Re: 2.5 MHz low pass fiilter uses no toroids, SMDs #ubitx

VK3HN
 

Good looking trace from a HPF made of surface mount inductors and capacitors. I'm not surprised by the use of s.m. caps but inductors does surprise a little.  I would have hand wound them on T37-2 (at a minimum).  Are they anything special Glelnn?  --Paul VK3HN.  

PS: I want a Rigol DSA815 (!)

Re: ubitx first power up

KM4TRT
 

Thanks folks for all your help.  I'll try the BFO route first, now that I know the approximate range, and if that doesn't work I'll mess with the IF

Andy.   KM4TRT

Re: RF power chain mods and improvements..

Nick VK4PP
 

Anonther thought: We could take out the 2 power chokes L8 and L9, strip them, stack them and bifilar wind them and use in the same way without having to buy an extra  FT50-43.

73 Nick

Re: RF power chain mods and improvements..

K9HZ <bill@...>
 

Pretty much... you and i are on the same page.  I use a little different PA transformer (61 material because ive found it to be more efficient) but otherwise basically the same. 

 

Dr. William J. Schmidt - K9HZ


On Jun 12, 2018, at 5:39 AM, Nick VK4PLN <nickpullen@...> wrote:

Dr. William, Same mods as me?
73 Nick VK4PLN

Re: ND6T AGC implementation for uBIT-X

Dennis Yancey <bigbluedry@...>
 

Just sent you PayPal for 2 kits of each... 
thands
72, God bless

Re: Spurs for Dummies? #ubitx-help

Tom, wb6b
 

Someone was good enough to email me and let me know the uBITX does seem to meet the -43DB down specification. So, I'm doing WSPR on 15,12 and 10M now. I did back down the audio drive level a little more, just as a precaution. 

However, now that I discovered a way to switch one more filter with the relays that are already on the board, maybe I'll try putting a 160M lowpass filter there.

Thinking about how to reduce the spur was fun though. Even pondered bypassing the 45Mhz filter when transmitting on 15, 12 and 10 meters, and using the 12Mhz chain all the way to the mixer driven by CLK#2. Looked like it required a couple of switchable hi-pass filters on the output filters and, therefore, an additional relay, so no panacea. 

Thought experiments are no substitute for breaking out the soldering iron and trying some things, but, thought or solder, this is the type of thing that makes this transceiver fun to have. 

Tom, wb6b

Re: RF power chain mods and improvements..

ajparent1/KB1GMX <kb1gmx@...>
 

makes sense to reuse parts where possible.

My experience with output transformers is more ferrite the better.
However the 2:4 turn transformers at 12-13V had very poor efficiency 
as in under 40% and a lot of heating and the linearity was also poor.
Didn't make any difference which device.

Note I  measure the current to the finals alone since the board provides
the separate feed.  As a result anything over 2A for 10W was deemed 
not good (under 50%) and with the 2:3 and 2:4 I was seeing typically
2.6to 3A again for only 10W out.   Going from 43 to 61 ferrite made little
difference if the ferrite was enough except at 80m.   A transmission
line transformer 1:1 hooked in with DC blocking caps (.1uf 100V)  as
a balanced to unbalanced was  remarkably good on a BN43-6802 at 10W.
Most cases of ferrite heating it was the wire or how it was wound had
a greater effect.

Allison

Channel to talk in

Richard E Neese