QUICK PICK REVIEW: AUGUST 2008
RCA ANT1500 VHF/UHF Panel Antenna
It’s flat, and it has a cool design. Does RCA’s indoor panel antenna deliver the goods?
The ANT1500 first came to my attention at NAB 2008, when RCA’s PR guy Dave Arland brought a pile of samples to the MSTV’s annual meeting. It’s an intriguing product, measuring about 11” x 10” by ¾” thick, and is intended for reception of both VHF and UHF TV signals.
This is also a passive antenna design. There are no additional amplifying electronics in the off-white plastic housing, which is good news for locations close by TV transmitters and not so good news for reception farther afield. The housing has two holes on its back side for wall hanging and there’s also a sturdy metal bracket that can be used to stand the antenna upright on a shelf.
Figure 1. RCA’s ANT 1500 looks good on the wall or on a shelf.
While the ANT1500 is large enough to contain a resonant UHF antenna array, it’s a bit on the small size for reception of high-band VHF channels (7-13), let alone low-band VHF (2-6). The sample I saw at the MSTV meeting was open for inspection, showing the etched-copper UHF and VHF antenna elements.
The VHF antenna element is actually a dipole with the two legs at angles to each other, resulting in a semi-circular polarized pattern. A similar approach was taken with the UHF elements. RCA has labeled this as a “multi-directional” antenna. According to the company, it can be hung or even laid flat just about anyplace and doesn’t need to be rotated to peak up signals.
Why is polarization important? TV broadcasters use two different types of signal polarization. VHF TV broadcast antennas are designed for circular signal polarization, similar to what’s used on direct broadcast satellites, while UHF TV antennas are usually set up for horizontal polarization.
When you add in the effects of multipath on broadcast TV signals, they can arrive at your indoor antenna with the original waveform pretty severely distorted! Is the ANT1500 up to the task of receiving them anyway? Let’s find out.
Figure 2a-2b. The test setup (left) and Radio Shack’s 15-1878 (right).
ON THE TEST BENCH
For my tests, I hauled out a few extra antennas to do side-by-side comparisons. The test location was my back deck, which faces northwest and has a line-of-sight path towards the Allentown-Bethlehem, PA TV towers, about 22 miles away. There are six stations from that market receivable at my house — three analog UHFs (WLVT-39, WBPH-60, and WFMZ-69), two digital UHFs (WFMZ-46 and WLVT-62), and one digital VHF (WBPH-9).
I also checked reception of analog and digital stations from Philadelphia. Normally, I can only receive one digital station (KYW-26) on the rear deck with passive antennas, and that’s not always a given. The path to the Roxborough TV towers from here is about 23 miles, but it’s over a ridge and through a tall stand of trees, which means a preamp or amplified antenna is usually required for reliable reception at ground level.
Figure 3. The ANT 1500 under test.
Figure 4. Kowatec’s CS-102.
I split the signal from each antenna and fed one leg to AutumnWave’s OnAir Solution HDTV-GT receiver, connected to my Acer laptop, while the other leg went to a portable spectrum analyzer to look at the signal waveforms. I also checked each signal for stability (ATSC) and signal-to-noise ratio (NTSC).
For the comparisons, I hauled out Radio Shack’s 15-1878 indoor VHF/UHF antenna (amplified), Terk’s HDTVa indoor VHF/UHF antenna (also amplified), and Kowatec’s CS-102 UHF panel antenna (passive). Why compare amplified to unamplified antennas? So I could see what additional gain was needed to lock up stations right on the edge of reception. Experience has shown me that, once you get 15 miles or so away from a transmitter, you usually need more gain in the receiving antenna and/or supplementary amplification to ensure reliable reception.
The test procedure was to place each antenna at two locations — atop my Vermont Castings grille on the SW side of the deck, and atop a plastic storage tub on a table at the center of the deck. I then performed analog and digital channel scans with the HDTV-GT, and logged all analog and digital stations received cleanly.
Figure 5a – 5b. Radio Shack’s 15-1878 oscillates! Now you see it (top) and now you don’t (bottom), next to the DTV signal from WBPH-9.
First of was the Radio Shack 15-1878, which pulled in four analog VHF and 13 analog UHF stations successfully. It also bagged all three digital stations from Allentown, plus KYW-26 from Philadelphia, without any signal dropout. This antenna uses a pair of collapsible whips for VHF reception and a rotatable loop for UHF. (The internal preamplifier isn’t of the best design, and I saw it oscillating at times on the spectrum analyzer.)
Terk’s HDTVa was next at bat and it did the best of all the antennas, pulling in four analog VHF stations and 14 analog UHF stations. It also locked up 9 digital stations from Philly and Allentown, although it didn’t receive WBPH-DT’s signal on VHF-9. This antenna uses a log-periodic UHF antenna that has much more gain than a loop, but it’s also a lot more directional.
Figure 6a-6b. WFMZ-DT as received on the ANT 1500 (top) and CS-102 (bottom).
The ANT1500 followed next. It performed identically in both locations, receiving a total of six stations, two on VHF and four on UHF and none of them digital. That performance would be comparable to a UHF bowtie antenna.
Finally, I set up Kowatec’s CS-102, and it fared just a bit better, logging three analog VHF and six analog UHF stations, again failing to pull in any digital broadcasts.
Next, I set up an “optimized” reception test for the ANT1500 and CS-102, positioning them much higher off the ground and using the spectrum analyzer to find the “sweet spot” for best digital reception. Once in this location, both antennas were able to pull in solid digital signals from WFMZ-46 and WLVT-62, but it was clear the CS-102 was the better performer as the received waveforms with this antenna were stronger and more level, as shown on the analyzer.
Figure 7a-7b. WLVT-DT as received on the ANT 1500 (top) and CS-102 (bottom).
CONCLUSIONS
RCA’s ANT1500 is yet another antenna design that tries to emphasize style over function. By that, I mean that the ANT1500’s flat, low-profile housing may look great on your wall, but its performance on VHF channels is compromised as a result. For any TV antenna to have decent gain and approach resonance, its dipole element must be at least ½ wavelength long at the desired frequencies, even if that dipole is bent, twisted, or looped.
For Channel 6, that requires about 70 inches, and for Channel 9, you need about 32 inches. The only way to compensate for this low-gain design is to have lots of signal level from the transmitter, so the ANT1500 is probably best used at locations 10 miles or less from a high-band VHF TV transmitter where the path is line of sight.
The ANT1500’s UHF element performs much better and is probably good for 15 to 20 miles with a line of sight path. Of course, the higher you mount this antenna, the better your results will be. My suggestion to the design folks at RCA would be to add a low-noise, high dynamic range internal preamplifier with moderate gain — say, 10 to 12 dB. That will make a big difference in performance.
