Sip = Pwr (dBm) - Attic Loss (est 13 +/- 6 dB) + Antenna Gain (est 5 dBd for ANT751) - Balun Loss (est 0.5 to 1.5 dB) - Balun-to-DistoAmp Cable Loss
Now compare these strong levels to the calculated Sip levels in the Overload Spreadsheet, line 68 (for SIX strong signals). I estimate Sip = -30 dBm (give or take a few or more dB) which would degrade the Spurious Free Dynamic Range on all except the lower Gain Winegard models....which MIGHT be marginal, depending on how much Attic Loss you REALLY have and inaccuracies in TVFool predictions.
HOWEVER, since manufacturer's aren't interested in providing meaningful overload specs for Distribution Amps, we really don't KNOW whether they are as good as the lower Gain Winegard Preamps....maybe....maybe not....
So it's worth doing a Trial and Error Test, inserting small amounts of attenuation prior to the DistroAmp. Since Intermodulation Distortion Noise levels are reduced by 3 dB or EVERY 1 dB of Insertion Loss, inserting a few dB of Attenuation, such as a spare RF Splitter (typ 3.5 dB Loss), will reduce IMD Noise by 10.5 dB....and a 6 dB Attenuator will reduce IMD Noise by 18 dB....which is probably more than is needed at your location so that the the weak signals are no longer degraded by the IMD Noise levels.
Edited by holl_ands - 1/25/14 at 1:30pm