I think I bought 3 transvertors - Parks K7AAD?

Discussion in 'VHF/UHF - 50Mhz and Beyond' started by KC7DDW, Nov 28, 2014.

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  1. KC7DDW

    KC7DDW Ham Member QRZ Page

    Today I came across 3 Parks Electronics K7AAD Nuvistor Cascode Convertors, K7JRL has some information, and a few trips to Dr. Google is not getting me anywhere.

    I have the following:

    Model 144-1 Two meter converter
    Model 50-1 Six Meter Converter
    Model 220-1 220MHZ COnvertor.

    I don't want to hurt these, but I am confused about how they work, power input etc, also Why does it say IF Output are these receiver only?

    Any additional information about how they work, what I can do with them would be awesome, I have a few later model HF Rigs and this would get me on 220 SSB!

    73 Rich
  2. KO6WB

    KO6WB Premium Subscriber QRZ Page

    These are receive only converters. This is a photo of the 144-1.
    Notice this one will not work as it sits. The crystal for the oscillator is missing.

    Hope this helps
  3. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I had a lot of Parks stuff in the mid-to-late 1960s and they were high quality, well-built converters.

    But as stated above, for "receiving" only.

    The IF for most was 28 MHz, but in some cases could be other bands.

    The just "down converted" VHF to HF using a mixer and preamp. Most had built-in AC power supplies, so you just plug 'em in.

    In terms of performance, they're likely about as good as modern stuff. Nuvistors were pretty good and could provide a 2 dB NF on VHF. Modern FETs can do slightly better, but it's unlikely you'd notice.
  4. W0AAT

    W0AAT XML Subscriber QRZ Page

    On weak signal VHF going from a 2db receive system to a .5 is a huge difference!
  5. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I think that's a common misconception that works only in a closed (lab) environment.

    Almost anyone has more than 2 dB of atmospheric noise on VHF until you get up to at least 432 MHz, or maybe higher.

    On the bench, I measure a difference in sensitivity going from 2 dB to 0.5 dB NF at 144 MHz (closed, shielded system). Once I connect an outdoor antenna, not at all. Atmospheric noise rules and masks either of those NFs. The band where I start seeing a difference I can actually "hear" is 1296 MHz (or above), where ATN is lower and antennas can be incredibly focused, such as using a dish.
  6. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page

    I have a relatively large collection of receiving converters.


    Within that collection, I have only 1 Parks converter, a 50-1. However, they are above average in performance. Probably, the most common VHF converters are those made by AMECO which include "regular" miniature vacuum tubes and Nuvistor type converters. The AMECO converters do a very good job and, for most amateur radio operation, are going to perform as well as the higher priced converters.

    Like WIK stated, on VHF and, at least the lower segments, UHF, the ambient noise is going to exceed any really low noise floor of the converter. In urban, and suburban, areas, the ambient noise floor is way beyond the noise figure of any reasonable receiving converter below around 1 GHz.

    Glen, K9STH
  7. W0AAT

    W0AAT XML Subscriber QRZ Page

    I disagree having used several different preamps from stock mirage brick to mirage brick with a highly modified preamp(.7db) to high performance preamps that have been measured below .5dbnf. It makes a difference because what happens to that signal just above your local noise floor in a noisy preamp and a quieter preamp? Quieter will give you a better S/N. And for modes copyable UNDER the noise floor like JT65 it makes an even larger difference.
  8. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    What kind of antenna(s) are you using? I never had a 2m antenna so narrowly focused that the atmospheric noise was below 2 or 2.5 dB. I guess with a dish aimed towards a quiet part of the sky, and above the horizon, might be possible.

    I have lots of ARR GaAsFET and MESFET preamps that on the bench measure <0.5 dB NF. Once an antenna is connected, the received S/N isn't any different at all when compared with my "barefoot" front ends that measure ~ 3dB at 144 MHz. Zero difference in S+N/N on the weakest beacons there are (barely detectible with any kind of front end).
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