[time-nuts] high rev isolation amps
Rob Sherwood.
rob at nc0b.com
Sun Mar 27 00:34:21 UTC 2016
I use two ZHL-32A buffer amps, the appropriate Mini-Circuits LPFs, and 20 dB pads into a 4-way Mini-Circuits combiner. I believe it is ports 2&3 that have even better isolation than a 2-way combiner. These buffer amps run on 24 volts, where the ZFL-500LN doesn't have the output capability to test 100+ dB radios. Some tests need a third signal source and complimentary buffer amp and associated items.
To test a K3S or an IC-7851, it also requires HP 8642A generators that have lower phase noise than these top of the line rigs. Even my 8662A generators are not good enough, though they were 5 years ago. Now add the Flex 6700 and the ANAN-200D, the RMDR performance of a hand full of rigs is amazing.
Unfortunately transmitter performance has not kept pace with receiver improvement.
It will be interesting to test the new IC-7300 DSR with knobs (and lots of menus).
Rob
NC0B
Sent from my iPad
> On Mar 26, 2016, at 6:00 PM, "jimlux" <jimlux at earthlink.net> wrote:
>
>
>
>> On 3/26/16 2:30 PM, Rob Sherwood. wrote:
>> You cannot add the directivity and gain. Doesn't work that way. Rob, NC0B.
>>
>
> Yeah, I kind of figured that after getting the S parameters from minicircuits.
>
>> Sent from my iPad
>>
>>> On Mar 26, 2016, at 2:00 PM, "jimlux" <jimlux at earthlink.net> wrote:
>>>
>>>
>>>
>>> Consulting the time-nuts hive mind here..
>>>
>>> I'm looking for off the shelf connectorized amplifiers with very good reverse isolation for doing things like intermod measurements (e.g. 2 signal generators followed by amps/pads into a combiner) and phase noise measurements for a digital receiver.
>>>
>>> 1-100 MHz kind of frequency range..
>>>
>>> I've used ZFL-500LN (30dB gain, 27 dB directivity in the data sheet, which I interpret as 57dB reverse) , ZX60-4016 (really more of a microwave amp, and not so hot reverse wise.. 25 dB)
>>>
>>> I'm not particularly cost constrained, so a higher power amp (which also reduces distortion products from the amp) followed by pads is always an alternative.
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