| Products > Test Equipment |
| ...Rohde&Schwarz ZVH4 tracking generator issue |
| (1/1) |
| VE2UM:
Hi... At my shop, we currently use a Rohde&Schwarz ZVH4 Antenna/cable/spectrum analyzer. We've been using this portable unit for almost 10 years... but... Two weeks ago, the ZVH4 shown an issue: Noisy s11 / Smith curves and mediocre isolation limits. I analysed the case to find a 50 dB weak tracking generator. On spectrum analyser, the ZVH shows excellent behavior (i can easily measure a -140 dBm signal on a 1 kHz span (30 Hz RBW)), so the "receive" side is no issue. However, in both "Antenna & Cable test" and "Network Analyzer" modes the tracking generator is about 50 dB down, greatly handicapping s11 / Smith measurments (noisy curves) and making isolation tests totally unuseable above a mere 40 dB. On "Antenna & Cable test", the tracking output is the same 50 dB down on both Port 1 and Port 2. Also, TG level (from 0 dBm down to -40 dBm) is linear (from -50 dBm down to -90 dBm). I opened the unit to take pictures to try to spot something revelant w/o success. Our ZVH4 being still useable, i did not go any further (no probing / signal level measurment) with the unit open. Notes: 1 - That ZVH4 RF board has SEVERAL SPDT RF switches, mainly 42551 (Peregrine Semi PE42551 9k - 6 GHz SPDT) and S50 / S60 (the nearest device i found on DK is SKY13298-360LF). 2 - Several S50 / S60's switches are used in cascade. I suspect that R&S used this arrangment for maximum port-to-port isolation. 3 - The "75" devices are probably also RF switches but i didn't want to remove the stickers for reliability purposes. Does anyone have worked with ZVH-4 ??? Do you have a service manual or, at least, "Thery of Operation" / block diagram ??? Thank you. Normand Martel VE2UM |
| VE2UM:
More pictures... |
| Navigation |
| Message Index |