[TenTec] Eagle 9MHz tap questions

Katz Ajamas ajamas.rn at gmail.com
Tue Dec 23 11:28:04 EST 2014

 I receive the list in digest mode so this may be a little disjointed.

> I think it's likely that updated schematics were not published.  Bob, what
> are you hoping to do with the 9MHz i.f. output?
> Barry N1EU

*What to do depends on where it is in the circuit. I want to learn and then
move if necessary. My thinking is to add a panadapter/second receiver but
without knowing the bandwidth I'm not sure if I want to use a 9MHz tap or
add a preamp and tap after the bandpass filters and before the mixer. *

*I'm considering the Afedri 12bit IQ receiver. It has 1850kHz bandwidth and
an ethernet port. It does not have bandpass filters so will benefit from
following those in the Eagle. At 80Msps, I'm not worried about aliasing,
just overload. *

*Among other alternatives is the $20 softrock board. Bandwith using it is
limited to that of the sound card employed. The sound adapter I have now is
48kHz. So, the softrock will definitely need a bandlimited signal. It will
also need a buffer amp to keep it's mixer noise out of the Eagle. How much
filtering to include depends on the signal available from the Eagle. *

*To learn what's at the port, I connected my general coverage receiver to
the "tap". Strangely, I did not find any down converted signals. I will
give it a try with a different cable, but I thought it odd that I could
tune as if connected to the antenna.*

*So, here I am. To aid in deciding if I will want to use it or add
something different, I would like to know where the "tap" is. I can always
have a look inside. I was just hoping to find in the documentation or from
someone who knows.*

> Is it just a tap, like perhaps a Y-connection, or does it also have a
> buffer stage?
> Unfortunately my Eagle fell out of the nest before that feature was added
> to the radio.
> 73 - Rick, DJ0IP
> (Nr. Frankfurt am Main)

Based on the description, there is no buffer.

> It is after the mixer and before the roofing filter.  I don't have the
> schematics handy where I am at, but I do recall it between those two
> segments.  I'll be back in my shack later tonight and can look at
> schematics then.
> 73 -EricW9WLW

> If I recall correctly, the early versions of the Eagle (which these
> schematics appear to have the dates for) did not have the IF output tap.
> ?There should be some newer schematics somewhere but they aren't on the TT
> website.
> Mike, WA1SEO


> There is a new set of schematics that wee release either in late 2012 or
> early 2013.  Sorry I'm not of more help, but it's intermission at the
> theatre I took my wife at so... No schematics here ?
> -Eric

Thanks! I would like to see these.

> I looked and the schematics are dated 9-2013, there is also the
> modification instructions available that should give direction on the
> whereabouts of connection points, etc.
> -Eric

The file is dated 2013. The schematics are dated 2010. Going by block
diagrams and photos...

The panadapter/external receiver modification is not a 9MHz IF tap. It is
between the output of the LPF board and the BPF/preselector. I can use the
Afedri here and on all bands below the one selected on the Eagle.

To use the Afedri and take advantage of the band pass filters I'm thinking
a tap with preamp(with T/R control) right after the BPF makes sense. The
Afedri does not have band pass filters which is not a big deal for a
panadapter...but if I want to use with CWskimmer, it will be subject to
less noise if after the Eagle BPF.

To use one of the Tayloe mixer to sound card kits for a panadapter, it will
be easier/cheaper to use the 9MHz IF.

I'm leaning toward using a $20 softrock board with added buffer and BPF on
the 9MHz IF and using the Afedri with an antenna matching network as it's
filter but want to study the Eagle a bit more first.

> Hi Bob-
>  I don?t have the answer to your question, but I too would like the
> physical answer. If you get an answer privately, myself and others would
> like to know.
> Merry Christmas and Happy New Year!!
> 73,
> Dave K1OPQ/4

No problem. If I end up digging in, I will post what I find.

> Are you going to add a panadapter ?

More interested in CW skimmer but pan kind of comes with that. The question
is. stand alone, with Eagle or try both :-)

> ================== K8JHR ==================
> On 12/22/2014 2:46 PM, Rick - DJ0IP / NJ0IP wrote:
> > Is it just a tap, like perhaps a Y-connection, or does it also have a
> buffer stage?
> > Unfortunately my Eagle fell out of the nest before that feature was
> added to the radio.
> > ____________________________________________
The mod TT published is a tap following the LPF board and may be installed
as a "Y" or in line if one wants to do some stuff to the signals before
shocking them back in the eagle.

> I was wanting to add a pan-adapter.
> I may have to replace a board in order to do that.
> My unit does not have the TMP jack with the 9 MHz out.
> Also I have to find a way to run the signal out the back.
> I already have two spare RCA Phono jacks in use for the pre-selector.
> 73 - Rick, DJ0IP
> (Nr. Frankfurt am Main)

Rick- Sounds interesting. Pre-selector in addition to band pass filters.
Less energy in the IF. If you have time, please tell me what you are using
and how. My older "boat anchor" receivers have narrow tuneable
pre-selectors so I am used to tuning with two hands

> The 9MHz i.f.tap as supplied by the factory may or may not give
> satisfactory results driving a panadapter.  My experience with the similar
> RX366 subreceiver were not entirely satisfactory - the passband was not
> flat and had some anomalies.  I ended up going another route.  Your
> experience might be different and if you try, please report back with your
> results..
> 73, Barry N1EU <osijek.osijek at os.t-com.hr>

OK. Will report back.

> I ended up adding the 9MHz i.f. output to the Orion main rx per the VE7TK
> mod instructions and the results have been quite good.
> With the RX366, there were two +15dB humps in my passband approx +/-25KHz
> from center freq.  Also, the rx signal levels seemed attenuated/compressed
> - for example, a signal that was 30dB above the noise on the receiver might
> show up as only 15dB above noise on the if output.  But as I said, it might
> be completely different on the Eagle.
> 73/Happy Holidays,
> Barry N1EU

There was a mention, in the section describing the tap, of the signal level
being 15db lower but nothing about change relative to the noise floor.

> Roger, tnx for the explanation Barry.
> A few dB wouldn't really matter but 15 dB is quite a lot.
> 73 - Rick, DJ0IP
> (Nr. Frankfurt am Main)

-Bob ah7i

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