Elecraft

PTT question

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Jim AB3CV

PTT question

I'm getting ready to add a RX array which includes remote preamps and an
NCC-1 phasing unit.

I'm planning on sending PTT to the NCC-1 which will in turn kill power to
the preamps. As I understand the manual upon key down the PTT line goes
active immediately followed by a default 8ms delay before RF.

Is that correct? The unstated part in the manual is that PTT is immediate
with key down.

If that is correct then that will satisfy the 5ms requirement of the
preamps.

Thanks

Jim ab3cv
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Jim Wiley

Re: PTT question

Jim -

Make sure your preamp(s) do not have internal electrolytic power
filtering caps. If they do, there is a fair chance the caps may hold
the preamp on long enough for it to suffer damage. But, I am wondering
why you are using preamps at HF at all? Unless the feedlines are
extraordinarily long _and_ you are talking 15 or 10 meters. We use a
NCC-1 here with the main and "sense" antennas 200 or 300 feet from the
shack, on 160, 80, and 40 meters, with no problems. Careful use of the
NCC-1's internal adjustable attenuators has solved any gain differential
issues so far.

- Jim, KL7CC

On 1/24/2015 1:17 PM, Jim Miller wrote:

> I'm getting ready to add a RX array which includes remote preamps and an
> NCC-1 phasing unit.
>
> I'm planning on sending PTT to the NCC-1 which will in turn kill power to
> the preamps. As I understand the manual upon key down the PTT line goes
> active immediately followed by a default 8ms delay before RF.
>
> Is that correct? The unstated part in the manual is that PTT is immediate
> with key down.
>
> If that is correct then that will satisfy the 5ms requirement of the
> preamps.
>
> Thanks
>
> Jim ab3cv
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>

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Jim Miller

Re: PTT question

These are short verticals. HI-Z AL24.

I'll ask about turnoff delay when I call DXE tomorrow.

73

Jim ab3cv

On Jan 24, 2015, at 5:43 PM, Jim Wiley <[hidden email]> wrote:

Jim -

Make sure your preamp(s) do not have internal electrolytic power filtering caps. If they do, there is a fair chance the caps may hold the preamp on long enough for it to suffer damage. But, I am wondering why you are using preamps at HF at all? Unless the feedlines are extraordinarily long and you are talking 15 or 10 meters. We use a NCC-1 here with the main and "sense" antennas 200 or 300 feet from the shack, on 160, 80, and 40 meters, with no problems. Careful use of the NCC-1's internal adjustable attenuators has solved any gain differential issues so far.

- Jim, KL7CC

> On 1/24/2015 1:17 PM, Jim Miller wrote:
> I'm getting ready to add a RX array which includes remote preamps and an
> NCC-1 phasing unit.
>
> I'm planning on sending PTT to the NCC-1 which will in turn kill power to
> the preamps. As I understand the manual upon key down the PTT line goes
> active immediately followed by a default 8ms delay before RF.
>
> Is that correct? The unstated part in the manual is that PTT is immediate
> with key down.
>
> If that is correct then that will satisfy the 5ms requirement of the
> preamps.
>
> Thanks
>
> Jim ab3cv
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>

Jim Miller

Re: PTT question

In reply to this post by Jim Wiley

Should have clarified: the preamps just match the short high impedence verticals to 75 ohms. Voltage gain is unity but obviously power gain.

Jim ab3cv

On Jan 24, 2015, at 5:43 PM, Jim Wiley <[hidden email]> wrote:

Jim -

Make sure your preamp(s) do not have internal electrolytic power filtering caps. If they do, there is a fair chance the caps may hold the preamp on long enough for it to suffer damage. But, I am wondering why you are using preamps at HF at all? Unless the feedlines are extraordinarily long and you are talking 15 or 10 meters. We use a NCC-1 here with the main and "sense" antennas 200 or 300 feet from the shack, on 160, 80, and 40 meters, with no problems. Careful use of the NCC-1's internal adjustable attenuators has solved any gain differential issues so far.

- Jim, KL7CC