[TenTec] 250Hz Roofing Filter

Zivney, Terry 00tlzivney at bsu.edu
Mon Jun 10 20:29:33 EDT 2013

The Orion 565 (aka Orion I) uses 250 and 500Hz filters previously used in the Omni line.

The Orion II 566 uses 300 and 600 Hz filters with lower loss and slightly different frequency so doesn't have the

extra amplification stage that is in the 565 Orion.  Using the Inrad 600 Hz filter in the Original Orion has a different center frequency than the 250 and 500 Hz filters and  doesn't use the extra amplifier, so doesn't have the extra noise.

Terry N4TZ

From: michael.cheponis at gmail.com [michael.cheponis at gmail.com] on behalf of Michael Cheponis [Michael at Cheponis.Com]
Sent: Monday, June 10, 2013 7:49 PM
To: Zivney, Terry
Subject: Fwd: [TenTec] 250Hz Roofing Filter

Hi are you also saying or implying that the 600 Hz Ten-Tec filter also has the extra IF amp and therefore extra noise?

Also, we're talking about quite low frequencies here --- couldn't the extra IF amp be replaced by one designed properly (to overcome the additional loss of the more-narrow filters, presumably)?


---------- Forwarded message ----------
From: Zivney, Terry <00tlzivney at bsu.edu<mailto:00tlzivney at bsu.edu>>
Date: Mon, Jun 10, 2013 at 3:53 PM
Subject: [TenTec] 250Hz Roofing Filter
To: "je2uff at gmail.com<mailto:je2uff at gmail.com>" <je2uff at gmail.com<mailto:je2uff at gmail.com>>, "tentec at contesting.com<mailto:tentec at contesting.com>" <tentec at contesting.com<mailto:tentec at contesting.com>>

Hi Toshi

The Orion 565 has an extra IF amplifier for the narrow 250 Hz Roofing filter, which adds noise.
Testing reported in QST showed that the dynamic range was worse with the 250 Hz filter than with the wider filters because of this extra amplifier.

A common solution used in the USA is to substitute a 600Hz roofing filter from International Radio (INRAD) in place of the standard 1,000 Hz roofing filter and use that instead of the 500 and 250 Hz roofing filters. Most of us have found that that 600 Hz filter is adequate for even the most demanding contest operation.

Terry N4TZ
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