Here's some info on available OTR DVRs:
Tablo
https://www.tablotv.com/Program guide requires subscription.
Can be used without program guide.
No HDMI out so content must be streamed to device.
No internal hard drive. Requires USB external drive.
==============
Channel Master DVR+
http://www.channelmaster.com/Antenna_DVR_s/336.htmProgram guide is free. Will acquire guide data from internet if connected, otherwise uses PSIP data from OTA signal.
16GB built-in storage which gives about 2 hours recording. External USB hard drive needed for longer recording.
==============
Magnavox MDR557H/F7
http://www.magnavox.com/product/product.php?id=151Only one tuner.
TV program is down-converted to standard definition prior to saving to hard drive or DVD.
No program guide.
==============
Tivo
http://www.tivo.com/All units require subscription for program guide.
Romio (for digital cable and antenna)
$199.99
4 digital tuners.
Guide subscriptions:
$14.99/month
$149.00/year
$499.99 lifetime
Roamio OTA (for antenna only)
$49.99
4 digital tuners.
Guide subscription:
$14.99/month.
As of May 29, 2015 $399.99 includes lifetime guide subscription.
https://www.tivo.com/roamioota2176==============
ePVision PHD-VRX2
http://www.epvision.com/HDTVSTB/phdvrx2main.htmDual tuners. Tuner-1 is digital and analog. Tuner-2 is digital only.
Can view ATSC, Clear QAM, and NTSC but only records digital ATSC and Clear QAM. Will not record analog.
Requires external USB drive.
==============
I own the following boxes:
Mediasonic HW180STB
http://www.mediasonic.ca/product.php?id=1377202059Single tuner.
Requires external USB drive.
Acquires program guide from PSIP data in OTA signal.
Sets clock to time data broadcast from station that it is tuned to. If the station is broadcasting incorrect time the recording will not start at the proper time.
iView 3500STB
http://www.iviewus.com/index.php/iview-3500stb.htmlSame as above.
Both boxes are virtually identical. They can be purchased on Amazon for about $35 plus the cost of a hard drive. They do the job but it takes a while to figure out the best way to do things.
I also have a PC running Windows 7 Media Center with two dual tuner SiliconDust HDHomerun boxes. Needs an internet connection for program guide. This setup works very well for me.
http://www.silicondust.com/Windows Media Center
Media Center was free with Windows 7 but costs extra for Windows 8 and Windows 10 will not have it at all.