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Author Topic: Argonaut 509 filter suggestion  (Read 4875 times)
KF4LXB
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Posts: 36




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« on: January 09, 2013, 11:28:30 AM »

Good afternoon all,

I recently purchased an Argonaut 509 which has been loads of fun so far. One of the things I would like to think about adding is a CW filter. The one in the radio is something like 2.5 KHz and that is dandy for SSB but I can already see the advantage of having a narrower one for CW, especially since my operating habits have been moving more and more in favor of CW. There seem to be a few options out there from MFJ, Vectronics and a nice looking kit from the 4 State QRP club (Hi-Per-Mite). If possible I would like to stay away from any heavy mods to the rig. If anyone has any suggestions or experience in this area it would be greatly appreciated.

72,
Christian KF4LXB
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Christian
Albemarle, NC
EM95
http://kf4lxb.blogspot.com
WB6BYU
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Posts: 13486




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« Reply #1 on: January 09, 2013, 01:14:38 PM »

Seems to me that Ten-Tec offered a CW filter option at the time, and there was
a set of RCA jacks on the back panel where it could plug in (thought it might
require the removal of an internal wire.)

This would allow you to insert the filter into the audio chain ahead of the volume
control (and possibly ahead of the AGC point), which makes the radio behave
much better when there is a strong nearby signal.  I'll have to dig out the manual
for my older 505 Argonaut to check.

That means that your external audio filter doesn't need to include an audio
amplifier and speaker, just the filter itself, which would play through the existing
audio system in the radio.
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WA2TPU
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Posts: 219




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« Reply #2 on: January 09, 2013, 03:18:41 PM »

To All......
The Ten Tec cw filter for the 509 Argonaut series was the Model 208 and it cost a WHOPPING $29.00 way back when. If you can find this filter....BUY IT because its a real decent add on made specifically for the 509.
Best regards and many 72/73.
Don sr. --WA2TPU --
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WB6BYU
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Posts: 13486




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« Reply #3 on: January 09, 2013, 04:51:59 PM »

I suspect that the circuit is about the same to the one I have in my Argosy, and
would be easy to reproduce if you can't find an original.  There are many good
circuit designs available that could be patched into the rig in the same way, but
likely would require building your own.

I'm not familiar enough with the commercial offerings to recommend one, or to
know which ones could be installed in this manner.
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W1JKA
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Posts: 1816




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« Reply #4 on: January 10, 2013, 03:41:52 AM »

    My Hi per-Mite results:I have built a few of these filters for my MFJ and SWL qrp rigs,a noticeable and positive difference to my ears from the stock filtering.I also tried one out on my K-1  and IC 7200.The three K-1 filters are excellent but with the hi-per-mite I notice a bit less QRN .The IC-7200 adjustable DSP filtering on cw is also excellent but I don't care for what I call a flatish tone on the cw note you get with DSP and by using the hi-per-mite it sharpens up the cw note to a more pleasant tone to my ears.In short they work for a 200 cycle width note.Mine are all used externally as the amplificaton in all my rigs is sufficient.For $19.00(ship.inc.) it's worth experimenting with and if it does'nt meet your expectations at least you will have fun building it.
« Last Edit: January 10, 2013, 03:52:08 AM by W1JKA » Logged
N2UGB
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Posts: 179




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« Reply #5 on: January 10, 2013, 04:46:50 AM »

Lucky you!. My happiest memories are of my 505/509/515 Ten-Tecs. Consider a used outboard MFJ audio filter. Same "box" and pretty much same results. Wish TT had decided their new QRP rig would be an updated repro of that desk-top TT QRP series Embarrassed Embarrassed.

73 de F8WBD
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KA1DBE
Member

Posts: 122




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« Reply #6 on: January 18, 2013, 05:04:04 PM »

I used an MFJ filter on mine when I first got it.  Found a 208 at a hamfest and snapped it up.
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W9CW
Member

Posts: 109




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« Reply #7 on: January 20, 2013, 06:07:34 PM »

The stock filter in the 509 is a 2.4kHz to 2.5kHz 4-pole xtal lattice filter.  Typically, if the 509 is sent in to Ten-Tec for any repair, they upgrade the filter to a 2.4kHz 8-pole xtal lattice filter.  Like the Triton series, 540, 544, and the original Omni D, the CW filters were audio filters only - no option for a 500Hz or so xtal lattice filter.  The Omni Series B and Omni C corrected that by providing a PIN diode-switched board for adding a narrower SSB xtal lattice filter (1.8kHz) and a CW xtal lattice filter (500Hz).

The early Ten-Tec rigs, including the Argo 505, 509, 515, and all those mentioned above, used audio-derived AGC - not I.F. AGC.  The Model 208 filter option for the 509 was an audio filter built with op amps.  However, unlike most other outboard audio amps that are used with the headphone or speaker outputs, the Ten-Tec 208 audio filter was within the audio-derived AGC loop.  Therefore, out of passband signals would not pump the AGC.  You can certainly use a 3rd party outboard audio filter (Autek, Datong, MFJ, et. al.), but they will not work as well as the Ten-Tec Model 208 outboard audio filter, as they are not within the AGC loop.

With my 509, I added the audio notch filter board from an original Omni series to the 208, plus there is one additional op amp filter BW that can be used with the stock 208.  You just need to change the position of the filter switch stop, and you will have a total of 4 audio filter BW positions, plus the notch filter should you add the board to the 208.  With this combo, the Argo 509 and 515 make excellent QRP CW rigs.
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