CB/10M stuff modification to other HF bands

Discussion in 'General Technical Questions and Answers' started by EA1BDF, Oct 22, 2016.

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  1. EA1BDF

    EA1BDF Ham Member QRZ Page

    Hi all.

    This is my first post here but I have been reading this page for a lot of time and i think that is very helpful to solve any problem that people have.

    I would like to know if it's possible to mod this gear to handle another bands that CB/10M bands (HF HAM BANDS).

    AMPLIFIER ZETAGI BV2001 MkIV

    Photo

    [​IMG]

    Schematics

    [​IMG]

    TRANSMATCH ZETAGI HP1000

    Photo

    [​IMG]

    Schematics

    [​IMG]

    Any idea would be welcome and very appreciated.
    Thanks in advance.

    P.S: sorry for my poor english.
     
  2. W9GB

    W9GB Ham Member QRZ Page

    This is a MONO-BAND sweep-tube amplifier (26-30 MHz range), more common in Europe.
    10-meter usage possible, without modifications/changes.
    HF radio radio amateurs prefer Multi-band HF amplifier.

    Thousands of these illegal CB/11-meter amps (poorly built) are parted out or trashed each year in North America. The AC transformers and glass tubes most valuable parts (electronics chop shops).

    This Zetagi model is rarely seen in North America. Discontinued product. Cheap glass vacuum tube production (sweep tunbes) in USA, Western Europe, Japan closed / shutdown in 1980s.

    ZETAGI is still in business (Italy contact information below).
    http://www.zgitaly.it/inglese/area.asp?sez=17&id=85

    The BV2001 uses the EL509 (6KG6) television sweep tube (Eastern Europe). NOTE: Audiophiles are now using a JJ /Tesla EK509-S (no top cap, can not use in BV-2001).
    http://www.radioaficion.com/HamNews/articles/2277-zetagi-bv-2001.html

    ZETAGI s.r.l.
    Via Ozanam, 29
    20863 Concorezzo (MB)
    Italy
    Tel. +39 039 60 49 346
    Fax +39 039 60 41 465
    info@zetagi.org
     
    Last edited: Oct 23, 2016
    EA1BDF likes this.
  3. N7EKU

    N7EKU Ham Member QRZ Page

    Hi,

    Sorry I don't have any experience about modifying tube amplifiers. But I have read a bit and know that you will also want to read older amateur radio handbooks and study their tube amplifier theory and construction chapters. For change to a single other ham band it could probably be done fairly easily with some inductor and capacitor changes on the input and output circuits. For multiple bands it will need more work with adding bandswitches etc.

    The tuner would also take a bit of work. The SWR detection cicuit is a transmission line type so it may not have the sensitivity to work on the lower bands. That would be a fairly easy circuit to change to a transformer type.

    The transmatch circuit would need some changes for sure. It looks like the capacitors would be fine to keep as is, but the inductor is a fixed value type and would need to be changed to a variable one, or a tapped coil with a multi contact switch.

    73,


    Mark.
     
    EA1BDF likes this.
  4. K8JD

    K8JD Ham Member QRZ Page

    Maybe 12M on a CB radio amplifier but you need to pad the capacitors with a fixed value or wind more turns on the coils.
    For lower bands you may not have enough room for bigger coils !
     
    EA1BDF likes this.
  5. EA1BDF

    EA1BDF Ham Member QRZ Page

    W9GB, N7EKU & K8JD, many thanks for your answers.

    I understand then that it would be difficult to change the gears behaviour to operate in another ham bands, so the only question I have if it is possible to use the transmatch capacitors to make a homebrew magnetic loop to work in these frequencies (10M - 80M). If not, I'll try to sell them to any CB operator.

    Capacitors

    [​IMG]

    Thanks again for your help.
     
    Last edited: Oct 24, 2016
  6. N7EKU

    N7EKU Ham Member QRZ Page

    Hi,

    Unless it was for receive only, I'd have to say no to converting the transmatch to a loop tuner. The two capacitors are not even transmitting types so even in their current use they are not good enough (probably they would start arcing under heavy loads even with less than even 100W since the spacing is so narrow). Loop tuners require even greater spacing than normal tuners and usually have to use special types like butterfly plate arrangement, or vacuum.

    So I think you would be better off selling it to a CB operator like you said.

    73,


    Mark.
     
    EA1BDF likes this.
  7. EA1BDF

    EA1BDF Ham Member QRZ Page

    Many thanks Mark, I appreciate your advice...
     
  8. WA7KKP

    WA7KKP Ham Member QRZ Page

    I'd skip the tube amplifer altogether -- they were usually built with parts that barely worked, and sweep tube finals are now very pricey from all those 11 meter hacks who tried to use "linears" for AM.

    The tuner is only useable on 11 meters, but may be okay for 10 meters by taking a turn or so out of the coil. Looking inside of it, you can see things are pretty lightly built, and I wouldn't dare pushing more than 10 watts through it. With a bit of scrounging, you could homebrew a smile L-match that would handel 100 watts, maybe more, and it would work on ALL bands, including WARC.

    One coil, with taps, and one variable capacitor of 220 pf or bigger, with a fair amount of plate spacing is all you need. Cabinet optiona.

    Gary WA7KKP
     
  9. W9GB

    W9GB Ham Member QRZ Page

    Luis -

    The Transmatch box and parts would be great for usage up to 100 watts or with a QRP station.
    Numerous designs on the Internet that would require minimal component changes.
     
  10. KM3F

    KM3F Ham Member QRZ Page

    Not knowing what the rules and Law is in your country, the amplifier could be 'improved' to better standards.
    Look at the input first.
    1. The tube is there to boost the drive from about 5 watts to a level the output stage can be driven to.
    Is you driver radio at the 5 watt level? If not that needs to be addressed.
    2. The input tuned circuits for using the amplifier over a wider frequent range need to be added to.
    Is the amplifier biased for SSB? Don't look so, made of AM only use as a Class C bias.
    3. The output tank would need to be added to or re-designed.
    The out put has no filtering 'if' harmonics are an issue with your Law.
    4. The components in the Transmatch are not up to handling the power level the amplifier would be capable of especially during mismatched tuning conditions.
    5. The tubes may be hard to find for replacement.
    Otherwise for what the amplifier was built for, the design and workmanship is quite good compared to the junk that was made here in the US.
    If you have no technical skills to understand what you need to do, I would abandon the project unless you want to use it to learn from.
    Good luck.
     
    Last edited: Oct 28, 2016

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