Dave, according to Panzer Tracts (if you build German armor, these are pretty much a must-have), the Panzerbefehlswagen IV had three antenna mounts and a periscope. The periscope was for observation and was located in a rotating mount on the 300 degree radian from the cupola, about where the old periscope was located on the PzKpfw IV ausf D. It was a very tall thin cylinder in appearance, and it was about three times the height of the cupola. This was stowed inside the turret.
The three antenna mounts were: the original PzKpfw IV ausf H/J mount with the 1.4 meter rod antenna on the aft left corner of the engine section, but this was used only for the Fu 7 transmitter/receiver used to communicate with Luftwaffe aircraft (otherwise, it was there but empty); the star antenna mount added to the rear plate inside the large armored pot, but this was used only with the Fu 8, used to communicate with ground units (otherwise, it most likely would have been empty, as tanks set up for aircraft use wouldn't have had the star antenna issued); and the antenna mount for the Fu 5 on the turret roof where the close-in defense weapon was placed on later PzKpfw IV Js, carrying a 2 meter rod antenna. As the Fu 5 was always carried, the turret roof antenna would have been seen on all these vehicles. For the others, you'll have to decide whether you want armored force commander or Luftwaffe communications.
According to Tom Jentz, there were 105 PzBflWg IV built new or converted from standard PzKpfw IVs, from March through September 1944. There does not appear to have been a stowage tube for the star antenna, though there was a square section beam carried on the top of the support brackets for the hull schurzen centered on the turret and about the same length. It is POSSIBLE this was a square-section box to stow the star antenna, but I don't know. It was there; you can model it without having to explain what it was for.
The Panzerbeobachtungswagen IV (133 built or converted from April 1944 to March 1945, but the first ones delivered appeared in July 1944) was an interesting vehicle. It was similar in many respects to the Panzerbefehlswagen IV except the PzKpfw IV cupola was replaced by the low cupola from the Stug III ausf G. The star antenna and rear antenna mounts were the same, and the periscope mounting was installed as well, but the turret roof antenna mount was moved to the far right turret roof in line with the hinges for the forward turret side door. This was to allow the installation of the close-in defense weapon. The coaxial MG 34 was removed from the turret, but the armored collar remained; there was no gun muzzle protruding. The Doyle plans for the PzBeobWg IV show all the antennas in use. Of course, the plans also show Ostketten and Thoma screen schurzen, which is impressive. Have at it and good luck. Send pictures....
