[TowerTalk] Receiver protectors and intermod, harmonics, etc.

[Jim Lux]

On 7/3/15 10:48 PM, Michael Tope wrote:
> On 7/3/2015 12:46 PM, Pete Smith N4ZR wrote:
>> Do the DX Engineering RG-5000 device, or the AS-RXFEP from Array
>> Solutions) behave nicely when hit with a signal well above their
>> protection threshold, or dothey generate interference (noise,
>> harmonics, intermod) from the energy that is blocked?
>>
>> Our particular application is for the RBN, involving a QS1R receiver
>> very close to the antennas of an HF ionospheric radar operating on a
>> couple of discrete frequency bands in the 8-18 MHz range with about 1
>> KW input (don't know what the EIRP would be at the location of the
>> receiver).
>>
>> Dx Engineering says their version offers "far lower harmonic and noise
>> products across the spectrum than any competing RX front-end saving
>> device,"  Would sure like to hear some impartial confirmation.
>>
> Pete,
>
> Do you have any information on the characteristics of the transmitted
> radar waveform (i.e. is it pulsed or FM-CW; if pulsed, what is the pulse
> width and pulse repetition frequency?).
>

if it's a ionosonde these days, it's probably either a long chirp with 
PN coding, but basically continuous. That's what 1 kW sounds like.. the 
older systems were 10s of kW with coded pulses using conventional analog 
pulse compression.

http://ulcar.uml.edu/digisonde_dps.html has a description of a specific 
system, but also discusses other systems.

if you're looking at an OTH radar, that's a different matter.