Wide band amp

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Re: Wide band amp

Post by Admin on Wed May 03, 2017 8:28 pm

Hi again, regarding the wideband amp,
I know that any TTL gate can be biased into the linear region by adding a single resistor between output and input, usually about 560 Ohms.

http://www.potatosemi.com have developed a TTL 74 series range of gates that will work at many hundreds of MHz. I think the name Potato Chip is a bit corny, but their site could be well woth a visit.

"Afroman" has produced a couple of projects on Hackaday, for example:
http://hackaday.com/2017/04/30/afroman-makes-a-uhf-oscillator-from-a-potato/

Just imagine if this is true and the potato chips are ready available! It would make GHz preamplifiers dirt cheap. I found this site by accident while surfing for tomething totally unrelated.

Best regards from harry - SM0VPO

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Re: Wide band amp

Post by Jalex2 on Mon Apr 24, 2017 4:14 pm

Hi Harry
I have seen prom burners pretty  cheap on the net for the older Eproms. 
I think I could burn them myself if I could just find the firmware for them
and I got one of those Nerd kits a while back and learned a lot programming
lots of different stuff for the microcomputer chips.  I have programmed on the computer since the old Commodore 64 days. I wrote a lot of games for it using machine code and they were really fast and made those old 8 bit computers really 
go. I stopped using machine code when it went 16 and 32 bit as C++ and Basic was a lot easier to troubleshoot.

I do most of my experimenting and testing with my Scope and now I have a new one and retired my old Tectonics. I got it mostly the help troubleshoot that
old Wurlitzer Organ as there are 100's of TTL chips in it and a lot of circuits to test
with very close tolerances.
It's a Siglent SDS1052DL and seems very good for what I do. It's really cool
to be able to just press a button and get all the data with out having to sit there with a pencil and calculate it. LOL

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Re: Wide band amp

Post by Admin on Mon Apr 24, 2017 2:17 pm

Hi Alex,
> I did find out what was wrong with my amp.
That is great. So glad you "tamed the beast". This is the sort of think I love with electronics. One always learns from mistakes, and that improves new projects.

Sorry you don't have a spectrum analyser. I always think that the most useful instrument was the GDO and the analyser comes in second place. 20 years ago thy would cost like US$50,000 but today you can buy a reasonable instrument for as little as US$1500, new (TTi PSA2701, Thurlby, UK). I paid $600 for my 3GHz analyser. At work I have gotten all the engineers new 6GHz handheld analysers.

I stopped playing the accordeon about three years ago, mainly because it is in Spain and I am mostly in Sweden. When I go to Spain I usually have to clean, repair, paint, mend, buy, and get cheated by workers, so I don't have so muct time to use the instrument. But I still live in hopes, and I still use the keyboard. At the moment I am trying to learn a little Beethoven on the piano.

> I  can't find the program data to burn onto them and ...
Ok, now I understand. I think I misunderstood, but now I remember a previous conversation. Ig you can get the SW then I can certainhly burn the EPROMS for you.

Anyway, gotta go now. Hafta buy more "fixit things" from the down. Also have the painters in to paint the whole outside of the house.

If you are listening on 14.175 this ifternoon I may be able to get on the bands, probably about 5PM Swedish/Spanish time :-)
BR Harry

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Re: Wide band amp

Post by Jalex2 on Sun Apr 16, 2017 6:32 pm

Hi
Harry
I did find out what was wrong with my amp.
It was the input. I had a 1meg resistor on it and that was causing my second op-map to rail. 
I put a 100k on it and now it seems to work pretty good. It wont go anywhere near 200 mhz 
but I don't think I need it that high for this.

No I don't have a spectrum analyzer as I don't normally do too much where I need one.  Yes I realize that one of the major problems is because of the way I built it
but I haven't decided on anything permanent yet. It's just on vector board now as I like to build that way when ever I can but it's just no good for RF construction. I have had very good luck building many LF circuits in this way.


This is cool. it sounds like your music skills are close to mine.  I started out years ago playing country music on the saxophone in taverns around here in the USA but never for big money and finally gave it up. LOL  I kind of followed in my dad's foot steps. He
drove truck and had a 5 piece band that played the dance halls every Saturday. I drove the big rigs for quite a while myself. I was kind of a late comer to electronics. Most of my schooling was from NRI( (National Radio Institute) correspondence courses.
I started right at the end of the valve Era. Did a lot of TV / VCR repair and got to see all the problems they had while redesigning them.
This organ I am restoring was his an that's kinda why I would like to get in running again.


As for the MC2716 I have a few of them too. The problem is I  can't find the program data to burn onto them and I can't get the data from mine as it's dead. 
They use to put these data files including the checksum on floppy disks 
and I thought it would by simple to find these files on the net but it looks like 
I was wrong.

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Re: Wide band amp

Post by Admin on Fri Apr 14, 2017 10:12 am

Hello Ivan,
Interesting on the keyboard.

When I was a kit I had piano lessons. My parents wanted a musical protégé and a kid who could play Beethoven's Für Elise in pubs an "make a mint". I got bored with repeating just one line of "Drink To Me Only" and other such boring stuff. I wanted to play Te Beatles. I packed it in.

The first piece I learned to play on the accordeon could have been easier. I locked myself in the workshop until I mastered "Hava Naguila". Today I also use a MIDI keyboard and Reason to create backing tracks for me on the accordeon. But it is not anything I do very often, especially as the accordeon is still in Spain.

> Certain distribution RF amplifiers have the "cascadable" statement in their datasheet.

Thats interesting. I was rather afraid that these things were pushed to their limit of stability, but it is good to have something to play with. I have to travel in a few days, but I will be back in a month and hopefully do some experiments then. I am quite looking forward to it .-)

Best regards from Harry

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Re: Wide band amp

Post by Ivan on Fri Apr 14, 2017 9:00 am

Hi both,
"I was thinking about possibly using two fo them cascaded"
Certain distribution RF amplifiers have the "cascadable" statement in their datasheet.
A proper decoupling and shielding must be necessary, of course.

"I can play well enough"
"I used to be able to knock out a tune or two on the accordeon"
As a child, I learned to play violin for 11 years. I was able to reproduce quite complicated
melodies that time. All that is forgotten now. When electronic keyboards became available
for me here in Czechia, I started with them. Now I play Yamaha PSR-S670, which is
a quite sofisticated instrument. I have huge problems playing the left hand parts in
bass clef. And I am lazy to attend a music school from scratch now. Sleep

BR from Ivan and happy Easter or Pesaach if you celebrate it !

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Re: Wide band amp

Post by Admin on Thu Apr 13, 2017 8:53 pm

Hi Alex,
> ... I pushed up the gain some more but now I am getting a lot of 60hz...
Interesting. Do you have a spectrum analyser? Sounds as though there could possibly be some sort of earthing problem and you have a loop. Maybe even self oscillation at higher frequencies.

What construction method did you use? I would have use dead-bug style with the ground pin soldered directly to the copper side of the board to ensure there is a good ground without inductance. Perhaps this is one of the reasons the gain is limited to 19dB? I was thinking about possibly using two fo them cascaded, but I think that stability could be a problem.

> ... uses 24 of the old MC2716 Eproms ...
I have an EPROM burner, and I may have a bunch of 2716 EPROMS at home. I will check that when I next go there. If you have a HEX file then send me a copy and I will see what I can do.

> I can play well enough to fix most of them if they like country music. LOL
I used to be able to knock out a tune or two on the accordeon. I made a bit of money at it, too, mainly by people wishing me to stop. LEL

Best regards from Harry

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Re: Wide band amp

Post by Jalex2 on Thu Apr 13, 2017 4:18 pm

Hi Harry 
I am interested in what you come up with after you get them.
Here's and update in my little circuit I pushed up the gain 
some more but now I am getting a lot of 60hz even though
it has a high pass filter on it. I think it's getting into the
circuit itself and not the antenna as I don't have it shielded yet.
I like experimenting in my free time so always interested in
new circuits and ideas. 

Lately I have been doing work on electronic organ consoles
and keyboards as this is a small beach town and people
hear don't want to ship them to Portland, Oregon.
I can play well enough to fix most of them if
they like country music. LOL

 
I still  haven't found the programs to burn to the prom chips 
on my old 1984 Wurlitzer in the back of my shop. It uses 24
of the old MC2716 Eproms. I have it completely restored
except for that prom chip and don't want to quit now.
 There is one with all the waveforms
on it that checks bad and so it doesn't work very well. LOL
I keep thinking they have to be out there but don't know 
where to look for them. the only other way would be to read
in a good prom and write to a new one.

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Re: Wide band amp

Post by Admin on Tue Apr 11, 2017 7:41 pm

Jalex2 wrote:Hi
Harry
That's a fantastic little IC. It says it's for Distribution Amplifiers.
... other uses too.
Hi Alex,
Yes, they are fantastic little chips. I have already ordered a couple of them. One of my working colleagues has used them and they came up in conversation the day after reading your post.

I want to find out how much power then can push. I was thinking about a VHF FM transmitter. At the moment I have a retro FM radio and a load of 50's / 60's CDs. The thought was I can stuff my stereo encoder into that, or maybe use the V5 and the chip as an amplifier. I saw that the supply current was well over 100mA, so it could mean that they have used a really Lo-Z to get the high frequency response. Perhaps it could mean a bit of usable power? 20mW @ 107MHz? Here's keeping the legs fingers crossed.

The high current is not so good far battery powered stuff, so don't throw away all your homebrew components. You may still need that junk box rabbit

Anyway, hafta go now. Yet another late night - just updated the homepages (www.sm0vpo.com - not sm0vpo.altervista.com)

Happy Easter - Harry - SM0VPO

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Re: Wide band amp

Post by Jalex2 on Thu Apr 06, 2017 7:55 pm

Hi Ivan
I looked at the spec sheet for them. 
That's a cool chip too. It looks like it just doesn't pay 
to horse around with  discrete  parts any more. LOL
I haven't looked around for RF chips much lately
as they used to be more than I wanted to pay and
hard to find and I don't experiment in RF too much.

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Re: Wide band amp

Post by Jalex2 on Thu Apr 06, 2017 7:34 pm

Hi
Harry
That's a fantastic little IC. It says it's for Distribution Amplifiers.
They have considerable more signal hitting them than I
would have from a short little antenna, Don't they?
I will still have to get one to play around with though.
I would think it could be designed into a band pass filter 
for other uses too.

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Re: Wide band amp

Post by Admin on Thu Apr 06, 2017 6:49 pm

Hi Alex & Ivan,
I see that Mouser have a broadband amplifier that covers DC to over 1GHz, TAT7457, and it costs just a few euros:

http://www.mouser.se/ProductDetail/Qorvo/TAT7457/?qs=mQhO0Mp9Jx%2f3yxipu1FvSg==

Is this the sort of thing you were looking for?
The output power is not specified, but the 3rd-order intercept point is +40dBm, and the gain of the device is 20dB.
Only three connections:
In - Gnd - O/P
(power fed via the output pin)

BR Harry - SM0VPO

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Re: Wide band amp

Post by Ivan on Thu Apr 06, 2017 6:44 am

Hi,
I had in mind something like MGA-82563 or MGA-64135. There are more similar parts on the market, try to google them. A challenge might be achieving the minimum frequency, as they are usually designed to work up from 100 MHz or so.

BR from Ivan

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Re: Wide band amp

Post by Jalex2 on Tue Apr 04, 2017 7:16 pm

Hi
Ivan
I have to get everything I use on line and I buy mostly from Jameco Electronics.
I haven't seen anything like that there.
Can you give me a mfg part number or a spec sheet link.
I am also not sure what would be a good input as I would like to keep the antenna 
as short as I can and still get the low end.
I am using a LM3914 Ic for the display set at 0 to 5v In and it works just fine.

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Re: Wide band amp

Post by Admin on Tue Apr 04, 2017 6:23 pm

Hi Alex & Ivan,
Interesting project. I have never tried MIMIC amplifiers but it is one of those areas I have always had "on the list" but never got "a round-twitt".

You are not trying to do the impossible. I once build an amplifier that covered about 10Hz to over 100MHz. It was basically a complimentart AF amplifier with "selected" transistors and loads of negative feedback. The feedback reduced the gain, but flattened the response.

I used the DC-coupled circuit with NFB so that I could add some reactive component to the feedback loop, but I never needed to use it. Reactive may have induced oscillations, but the un-modified amp was quite stable.

Just throwing in my two-penneth :-)

Best regards to you bolth from Harry


Last edited by Admin on Tue Apr 04, 2017 6:25 pm; edited 1 time in total (Reason for editing : it seemed like a good idea at the time)

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Re: Wide band amp

Post by Ivan on Tue Apr 04, 2017 6:37 am

Hi,
some MMIC amplifiers have a very wide frequency range. Did you consider using some of them?

BR Ivan

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Wide band amp

Post by Jalex2 on Mon Apr 03, 2017 3:50 pm

Hi
I may be trying to do the impossible.
What I have been trying to do is get high gain from 200hz. to around 100mhz.
I have used a high pass filter in the input to remove the 60 hz.
I don't have a frequency generator to cover a range like that so I  have been 
just trying to detect the power supply from my fluorescent bench light that
I suspect is somewhere between 50-100 Khz. There are no AM radio stations
in my area so I am not worried about that. I have gotten a rail to rail response
up to about 6 feet away from it but some how I don't think that's good enough.
I was trying to make something like the paranormal investigators use they call
EMP meter as I thought it might be fun to play with and have other uses too.
I tried a 5 transistor DC coupled amp and an LM358 with similar results.   
Can that be done and if so where can I find circuit for something like that.

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