Gary,
The last four hf transceivers that Ten-Tec built did not have that keying loop
you described.
IMO "most" of the transceivers on the market today do not have that keying loop
that you described.
Hundreds of members of my contest club will cringe at the thought of switching
with PIN diodes, even at 100w.
Here in Europe on large antennas at night on the low bands, especially 40m, PIN
diodes can partially forward bias and create IMD products.
All the strong arguments you hear from engineers in favor of PIN diodes are
coming from the states, not from the engineers in Europe. A reed relay is a
better option.
Apparently I am "holier" than most hams because I have never hesitated to drill
a hole in the top of my brand new car to mount my UHF antenna, nor to drill a
hole in the radio, especially in the back panel. When I do modify a radio, it
is well documented so that anyone who owns the radio later (and still has the
manual) has no problem to see what was done.
Ten-Tec did not deny service to modified radios.
Not sure what their current position on that point is, though.
In the day and age of the need to switch many devices between TX and RX, as
well as the fear of most hams to make the slightest little mod to their
precious radio, it is time to strongly consider using an external keyer rather
than the transceiver's built in keyer.
There are external keyers with multiple keying jacks each with adjustable
timing and even hang delay for the amp, if so desired. This is the only way I
see to have your cake and eat it too.
On the mod bit, THANK GOD hams 20 years ago did not have that silly opinion.
Yaesu sold an awful lot of FT-1000 xx transceivers and for the first 8 years
(at least) with horrendous key clicks. A $3 mod to the radio designed by W8JI
easily fixed it, yet Yaesu refused to do so until their 3rd version of that
radio came out. These were so bad, when used with an amp, they could easily be
40 or 50 kHz wide. Luckily hams modified [almost] all of them. It is rare
now days to find one that was not modified unless the original owner did not
work CW. BTW, ICOM had the same thing with their IC-202 and IC-402
transceivers, but the mod curing it was published in every ham mag around the
world.
BTW, the mod I describe is not only usable with an external preselector, you
can also use it to insert noise cancelors such as the ANC-4, without the need
to switch it in and out during RX and TX.
73 - Rick, DJ0IP
(Nr. Frankfurt, Germany)
-----Original Message-----
From: TenTec [mailto:tentec-bounces@contesting.com] On Behalf Of Gary F
Sent: Tuesday, September 13, 2016 5:04 PM
To: Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] Scads of used Icom IC-7300
I agree that RF sense is sort of risky with fast CW. It's not even ideal for
SSB but is tolerable. Lots of accessories, even some power amplifiers have used
it (for example, most 2 meter amplifiers).
If you are using Ten Tec transceivers, recent ones anyway, you would not be hot
when using the PTT line for switching because you would use the closed loop
keying that Ten Tec has already implemented in their radios. You would never
hot switch because no RF could flow until the switching relay was closed. If
you are using a QSK linear, you would route the "relay closed" feedback from
the linear to control the RF permission for the XCVR. The linear would be keyed
by an output from the preselector so that, at no time would there be RF on the
preselector until all relays were in proper position.
The relays in the preselector need not be heavy clunky things so they should
change quickly. They could even be PIN diodes at 100 watt power levels.
As you may know, I am not a be fan of drilling holes in chassis of commercially
made equipment. Not only are warranties voided, but she repair facilities will
not even service modified radios.
Also, being a radio reseller, I cringe when I have to explain away such added
holes and jacks to a potential buyer.
Gary
Sent from my iPad
> On Sep 13, 2016, at 8:33 AM, rick@dj0ip.de <Rick@DJ0IP.de> wrote:
>
> But that was yesterday.
> What do people do today?
>
> I'm not a fan of RF sensing. Hot switching? No thanks.
> You may get away with it in SSB but not in CW.
>
> 73 - Rick, DJ0IP
> (Nr. Frankfurt, Germany)
>
>
>
> -----Original Message-----
> From: TenTec [mailto:tentec-bounces@contesting.com] On Behalf Of Gary
> J FollettDukes HiFi
> Sent: Tuesday, September 13, 2016 3:07 PM
> To: Discussion of Ten-Tec Equipment
> Subject: Re: [TenTec] Scads of used Icom IC-7300
>
> Several preselectors were produced by commercial vendors, some time ago, not
> likely as good a preselector as yours, but they offered RF sensing to pass
> the TX signal around the preselector.
>
> This seems to be a better solution than modifying the radio.
>
> For those not comfortable with RF sense switching, one might consider using
> the PTT line to switch around the preselector.
>
> With most TT radios, these lines are very fast (for QSK) and could be in
> parallel with the linear key line if a linear is used.
>
> ‘Gary
>
>
>
>> On Sep 13, 2016, at 5:55 AM, rick@dj0ip.de <Rick@DJ0IP.de> wrote:
>>
>> Correct, my pre-selector is RX only, which the name implies.
>> That is why every transceiver I have had since the mid 70's was
>> immediately modified with two RCA phono jacks mounted on the back. I
>> interrupt the RX ANT line internally and run it thru the two jacks,
>> jumpered of course when no preselector is attached. Even my Eagle
>> has this mod. The OM7 had it available but very few people performed
>> the mod. I did it on the OM7 I tested here prior to its announcement
>> and it made a WORLD of difference on 40m.
>>
>> 73 - Rick, DJ0IP
>> (Nr. Frankfurt, Germany)
>>
>>
>>
>> -----Original Message-----
>> From: TenTec [mailto:tentec-bounces@contesting.com] On Behalf Of
>> shristov
>> Sent: Tuesday, September 13, 2016 10:15 AM
>> To: Discussion of Ten-Tec Equipment
>> Subject: Re: [TenTec] Scads of used Icom IC-7300
>>
>> "rick@dj0ip.de" <Rick@DJ0IP.de> wrote:
>>
>>> However the Dunestar SPECS on their web site claim 40dB band-to-band
>>> rejection. I was just quoting the specs.
>>> http://www.dunestar.com/store/Single-Band-Bandpass-Filters-pid-4.htm
>>> l
>>
>>
>> Hi Rick,
>>
>>
>> that's what I had in mind.
>> Taking the 7 MHz filter as an example, there is 40 dB attenuation on
>> ~3.5 MHz.
>>
>> But on 6 MHz the attenuation is practically nil.
>>
>> Your preselector is the right tool for the job.
>> But it's receive-only, given the 7.5 dB passband attenuation.
>>
>> Dunestar etc filters must have a much wider passband in order to
>> achieve low enough passband attenuation, making them suitable for
>> transmitting.
>>
>>
>> Best 73,
>>
>> Sinisa YT1NT, VE3EA
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