VCO Output is heavily dropping

[@Pra]

Am using VCO (POS-400+) to generate a fixed 300MHz signal.
This VCO output is connected to an Attenuator (ZX73-2500+ ) and the attenuator output is further fed to a RF Amplifier (ZHL-1-2W+) all with supporting electronics for controls.
This has been working fine. (all components are Mini-Circuits make)

Now, my application demands that: I use that same VCO output signal (300MHz) to feed to another attenuator (in parallel to the above) and another RF amp (ZHL-1-2W) is connected to the output of this second attenuator.

ISSUE:
While I am connecting in this mode, the output of the second RF amplifier is heavily dropping to ~10% of its normal expected output while the original RF amp drop is marginal. As I realized, this is due to the VCO output itself is dropping.

QUERY:
1) Is there an issue in the design ?
2) Any remedies/corrections recommended viz: matching issues?
3) What could be the reason for this drop in signal & how to correct it?

Please provide technical help or recommend suitable help centers/ websites.
Thanks.

 

[BigBoss]

How to connect the Attenuators in Parallel ?
If you drive 2 Power Amplifiers Independently , you have to divide the VCO Signal by 2 first then you can use attenuators etc.

 

[barry]

I’m assuming the VCO output is 50 ohm. If you connect two 50 ohm loads in parallel, that’s 25 ohms and of course you’ll see your output drop.

 

[biff44]

have you sniffed around with a spectrum analyzer to see if one of the amplifiers is oscillating on you?
have to probed the DC voltages to make sure they are not drooping when the RF output droops?