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Old 29-Apr-2016, 4:10 PM   #98
tripelo
Senior Member
 
Join Date: Jan 2010
Location: Dallas, TX
Posts: 123
Compare Received Signal Strength of 5 UHF Antennas

A series of antenna tests were conducted on April 14, 2016.

Objective: Compare performance of selected UHF antennas while receiving DFW TV channels

Antennas:

1. Antennas Direct 91xg
2. Solid Signal HDB91x
3. Channel Master CM-4228 (old version)
4. Antennas direct DB8 (non-e version)
5. Terk HDTVi (as reference)

Images of antennas at test location in a following post.

Test Location:

Garland, TX, ~30 miles line-of-sight to 27 DFW stations, located within +/-3 degrees azimuth.

Test location TVfool info posted earlier:

Compare Preamplifiers - Test Procedure & Configuration

Test Equipment:

1. Sencore SLM1456 – Signal Level and MER measurements
(Scans channels one-by-one, dwells a few seconds per channel to lock and obtain a signal average, total scan time for 27 channels ~6-7 minutes)
2. DG8SAQ Vector Network analyzer -VNWA
(Measure scattering parameter S11 (complex input impedance->return loss/SWR)
3. Belden Coaxial Cable 1694A (40 feet)
4. Ferrite Cores at Coax to balun/antenna connection (Qty=4)
5. Balun for CM4228 (homebrew, hand-wound ferrite core, measured loss <1 dB)
6. Push-Up Telescopic Mast, 25+ ft.

Test Procedure

1. Calibrate VNWA, with the 40’coax cable (refers measurements to antenna/balun connection).

Starting with Terk HDTVi antenna:

2. Mount antenna w/coax and ferrites to mast, raise center of antenna to 25 feet
3. Align antenna for peak signal on Channel 29 (~central angle to DFW stations)
4. With 1456 scan all DFW UHF stations for signal strength and MER (record times)
(repeat scan, while in this configuration)
5. Take at least 2 Photos
6. Turn antenna ~90 degrees, disconnect coax from 1456, connect to VNWA
7. Measure S11 (input impedance, SWR/Return Loss) for the band
8. Lower Mast remove antenna
9. For each antenna repeat steps 2 through 8, finishing with a repeat of HDTVi antenna.

The test location and setup was similar to that described in previous posts:

Televes DAT-75 vs. Antennas Direct 91XG

UHF Signal Strength vs Antenna Height (AGL)

Compare Preamplifiers - Test Procedure & Configuration


Compared to previous tests, some differences in equipment, this test:

- No attenuator was used,
- Sencore SLM1456 instead of SLM1456CM
- Others, VNWA, etc.


Credit:

Forum member re_nelson provided much appreciated assistance throughout test planning, test, and follow-up.

RE_nelson also:

- Provided most of the antennas
- Provided the Sencore SLM1456
- Aligned antenna, operated the SLM1456, performed scans, & collected data.

Image below: RE_Nelson at the antenna test station with his Sencore SLM1456.





The antenna mast is at far left behind the ladder and porch post. To aim the antenna, re_nelson observes SLM1456 and hand rotates antenna mast to maximize the signal strength indication.

(To be continued)

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Attached Images
File Type: jpg re_nelson at Test Site.JPG (82.4 KB, 1565 views)
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