Bias design, amplifier design, filtering etc.

[bob85]

i will have a look at that ken, see if i can get my head round it,

dwb good link, thats how i see it, you can see the texas star/fatboy circuit at the top through to a regulated circuit at the bottom.:sneaky2:

 

[bushwacker]

I just wanted to add in an update

I tested the bias on an old Palomar tx75 last night ( I removed the passive bias...I know someone will ask). Transistior were 2x srf2072. Everything went pretty well....I set the idle at around 130ma.
I excited the amp with a radio insted of signal gen. I just watched the output power and current draw of the amp to see if it was changing class.
It seemed to be doing the job. Unfortunatly I have a power supply problem with my scope and I cannot check the waveform.

Its still not done..but at least I was able to somewhat verify that it was working.

Bob...thats one hell of an urge...the microwave. Hopefully you got over it by now

Good link DWB

 

[bob85]

ken, is the circuit you have in mind the same as me using my ci power supply to bias the transistors or do you have something else in mind, maybe making the rf transistors an integral part of the constant current setup?

 

[bob85]

change of plan bush,
i am now looking for a scrap washing machine to build a watercooled bigbox,
seems straightforward enough, they have a 5kw heater fillament, tubes, a pump and an excellent all stainless low magnetic rf deck in an attractive case that fits in well with other electrical goods around the home ( the wife will even like it ) i think it would make a nice addition to any ham or cb radio operators home,
been able to watch the warm fuzzy glow through the toughened glass cabinet front will be a real talking point for visiting radio ops friends and family,

boo said he can wire the program dial as a warmup timer and stepstart, he says when it hits spin its ready to key,
if i go down that route i will need matching dials from other washing machines for the bandchange switch and the plate/load controls so it dont look out of place, i dont want odd looking controls,
i have seen washing machine dials with different load settings marked around the edge and a similar dial on a dishwasher in my wifes aunties kitchen with plate settings, its strange how radio folk notice things like that,
both would be ideal for this project and keeping inline with the wifes tastes in electrical goods,

i have some parts in the garrage but not everything i need to finish the job,

parts i still need to find,

a grid for the grounding
none conductive heat exchanger >275,000 btu
none conductive high dielectric pipework to fit the pump
large squirrel blower (20hp)
water conductivity meter with alarm shutdown trigger output ( industrial )
200 litres/52.8 us gallons distilled water
replacement door seal > ( special ptfe/ microdynema composite from wash & blow in the netherlands )
vacume variable > 50-400pf 50kv x2
vacume antenna relays 40a x 2 ( russion )
copper pipe ( i do my own plating )
ptfe barstock 2" x 3 feet
bigass transformer
none foaming detergent


i hope to post results here on the forum

 

[ken white]

ken, is the circuit you have in mind the same as me using my ci power supply to bias the transistors or do you have something else in mind, maybe making the rf transistors an integral part of the constant current setup?

Bob, if you tell me what idle current you want, I will design an op-amp driver to connect/control a series pass transistor. Or if the idle current is low enough, a simple JFET cicruit can be added to the output stage of the existing voltage regulator circuit if the voltage can be cranked up.

I look forward to your big power linear amp write-up!

 

[bushwacker]

change of plan bush,
i am now looking for a scrap washing machine to build a watercooled bigbox,

believe it or not...but I remember seeing a picture of an amp built inside a dryer or washing machine..... I think it was a washer
Somebody posted on a forum years ago.
I don't think it was as fancy of a design as you have planned

looks like you got it planned right down to the non foaming detergent

.....and I could just tell the wife I'm doing laundry when she gets on me about spending to much time in the radio room.
...there might be a market for this Bob

 

[bob85]

ken, most of the amps i see are directly connected in pairs to the input and output transformers, no capacitive coupling, i would need at least 200ma idle current per pair of transistors,



bush can you remember who that was with the washeramp, id like to compare notes with whoever has done it before,
i have seen two clean looking machines at the local tip, asked the guys to set them to one side while i decide if i want the 800 or 1100rpm spin speed, the zannussi 1100 has a lovely looking cabinet but the dials and such on the whirlpool look more suitable for radio use,
maybe i should take the wife down there and let her choose, it may boost her enthusiasm for the project, she's not too keen at the moment but im working on her, big bunch of roses waiting for her return from work, she wont have the heart to say take that shit back to the tip

 

[-=PEAKABOO=-]

some good reading here

VHF/UHF Long Yagi Workshophttp://www.ifwtech.co.uk/g3sek/tr-bias/tr-bias1.htm

Good read, I played with this years ago and had issues with the circuit working correctly. It looks good on paper but some of the values that you calculate do not work. A little tweeking and it will work though.

 

[bushwacker]

Hey Bob...
I'm still hunting that picture of the amp in the washing machine...
While looking for it, I stumbled on this old thread.

Check out Nomads pic.
www.worldwidedx.com/tech-repair/23467-where-your-amplifiers.html

I'm sure you will remember it.

 

[DIRTYWHITEBOY]

this?

 

[mackmobile43]

Hey Bob...
I'm still hunting that picture of the amp in the washing machine...
While looking for it, I stumbled on this old thread.

Check out Nomads pic.
www.worldwidedx.com/tech-repair/23467-where-your-amplifiers.html

I'm sure you will remember it.

Ask paws

 

[bushwacker]

this?

That might have been it.
I remember someone posting the pic a couple of years back.
Thats more than likly the picture.

Thanks DWB

 

[bob85]

lmao:w00t:

 

[BOOTY MONSTER]

this?

that should put out a CLEAN SIGNAL !!! hehehehehe hahahahaha hohohoho

 

[-=PEAKABOO=-]

this?

That thing will have a tendency to oscillate during the spin cycle, if you run on the delicate cycle it is a little easier on the load and seems to smooth out any wrinkles. The main problem with it is that you have to use a noise canceling microphone because the damn thing will produce a lot of back ground noise.