I've been using the Zoom H4 for some years now, but lately I'm having trouble obtaining clean stereo sound or clean mono sound to two seperate radio mics connected to L & R XLR ports (Zoom internal stereo mic turned off with Zoom set to Input 1&2)).

I normally use a Sony WRR-805 UHF Tuner connected via an XLR cable to one left XLR port which sends a signal to a Sony WRT-805 Transmitter that has a Sony clip mic. This produces good sound in either left-sided Mono or Left & Right Mono-Mix.

I will also regularly plug a Sony DC-78 (DC Power Supply Unit) into one of the Zoom H4 XLR ports and plug a wired clip mic directly into the DC-78. This produces decent sound for when I'm filming with a DSLR and need to record my own voice at the same time.

If I plug a Sony WRR-805 Wireless Tuner into the left XLR port of the Zoom, and a Sony WRR-810 into the right XLR port of the Zoom, and set both on same frequency to pick up a single clip mic connected to a Sony WRT-805 transmitter, it will produced beautiful clean and strong sound in L & R channels of the Zoom H4.

The problem comes when I want to record two seperate people at long distances from the camera & Zoom H4.

If I do the same as above, but bring into the equation a second Sony WRT Transmitter, things go wrong.

I connect a Sony WRR-810 and WRR-805 into left & right XLR sockets of the Zoom H4 in hope that they can pick up two people at different distant points, each wearing lapel mics wired to two seperate Sony WRT-805 units. (So that is four Sony units in all - a pair of senders and a pair of receivers).

The result when everything is turned on, provides just a high-pitched sound if all on same frequency. If I click one pair of the WRR & WRT units onto a different frequency, there will be decent pick-up on one mono channel and distorted on the other channel.

So, to the main question, is it possible to use two seperate pairs of wireless receiver & sender units with the Zoom H4 so it will pick up two different radio lapel (lav) mics at the same time as you are recording?

If the same set-up is used with a Canon XL2 or XL-H1 camcorder with two wireless units plugged into the rear XLR ports it picks up two radio lav mics no problem...so why not with the Zoom H4?

I suspect there's nothing unique to the H4 that's creating this problem.

First thing I'd work on is greater separation of frequencies between the two pairs. Somewhere I have a chart Sony included with these units, I'll see if I can dig it up. The point is that the freq that you set on a transmitter/receiver pair is the center freq. In operation, bandwidth is used on either side of that center frequency.

As a consequence of this, you need some significant separation of center frequencies between multiple trans/rec pairs. It's been a few years now, so I'm not remembering how much. But, just switching one pair to the next higher/lower freq is too little of a change, you need greater separation.

Will look for Sony's chart...

EDIT:
Ah, found a reference. You want a minimum of 1.125MHz separation, but more can help and won't hurt.

Of course if there's another source splashing RF onto your channel, it can create all kinds of interference. To check for this you'd listen to the receiver with the paired transmitter turned off. That's also a way to check for interference between units - with Trans A and Rec A turned on and working, try listening to Rec B - you shouldn't hear anything. With Trans B and Rec B turned on, you shouldn't hear anything on Rec A.

Cheers for the help Seth. That might be part of the problem. I'll try a much wider MHz frequency between both sets of units and see if it works.

Sometimes, the obvious is forgotten and all it takes is a very small yet vital change to make everything perfect.

I've just gone back and widened the frequency range differences of one of the sets of Sony wireless units, even further than they were before, and it has fixed the problem.

A series of tests with the four wireless units - two Sony WRT and two Sony WRR - connected with two seperate Sony lav mics in combination with a Zoom H4, all now work perfectly. The Zoom now provides nice and clean, strong stereo or mono sounds into both L/R channels.

This will hopefully come in very useful for long distance wireless recording with two different subjects at the same time, during my next major filming projects.

Thank you for the great help, Seth! Your small snippets of advice have helped prevent me from pulling more of my own hair out in frustration... :)

All right! Glad that helped.

For me, pulling more hair is no longer an option...

I was doing a Doco with the tallent coming down the river on a paddle steamer with the camera and crew on the river bank and did a double mic for the recording, one was a Sennheiser radio mic (to mixer then to the camera) the other was a lapel mic into a H4n which was placed in the talents jacket pocket in record mode.
The radio mic was marginal for the recording because of the range but the H4n was brilliant, I am going to use the setup of the recorder in the pocket more often.

The clip mic + H4 in pocket works well (I often use the Sony DC-78 + Sony 77b for this) for one person, but it would need two H4's for two people in different zones.